feat: Add admin vehicle management and profile vehicles display (refs #11)

- Add GET /api/admin/stats endpoint for Total Vehicles widget
- Add GET /api/admin/users/:auth0Sub/vehicles endpoint for user vehicle list
- Update AdminUsersPage with Total Vehicles stat and expandable vehicle rows
- Add My Vehicles section to SettingsPage (desktop) and MobileSettingsScreen
- Update AdminUsersMobileScreen with stats header and vehicle expansion
- Add defense-in-depth admin checks and error handling
- Update admin README documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/pages/SettingsPage.tsx

@@ -9,6 +9,7 @@ import { useUnits } from '../core/units/UnitsContext';
 import { useAdminAccess } from '../core/auth/useAdminAccess';
 import { useProfile, useUpdateProfile } from '../features/settings/hooks/useProfile';
 import { useExportUserData } from '../features/settings/hooks/useExportUserData';
+import { useVehicles } from '../features/vehicles/hooks/useVehicles';
 import { useTheme } from '../shared-minimal/theme/ThemeContext';
 import { DeleteAccountDialog } from '../features/settings/components/DeleteAccountDialog';
 import { PendingDeletionBanner } from '../features/settings/components/PendingDeletionBanner';
@@ -36,6 +37,7 @@ import PaletteIcon from '@mui/icons-material/Palette';
 import SecurityIcon from '@mui/icons-material/Security';
 import StorageIcon from '@mui/icons-material/Storage';
 import AdminPanelSettingsIcon from '@mui/icons-material/AdminPanelSettings';
+import DirectionsCarIcon from '@mui/icons-material/DirectionsCar';
 import EditIcon from '@mui/icons-material/Edit';
 import SaveIcon from '@mui/icons-material/Save';
 import CancelIcon from '@mui/icons-material/Cancel';
@@ -53,6 +55,9 @@ export const SettingsPage: React.FC = () => {
   // Profile state
   const { data: profile, isLoading: profileLoading } = useProfile();
   const updateProfileMutation = useUpdateProfile();
+
+  // Vehicles state (for My Vehicles section)
+  const { data: vehicles, isLoading: vehiclesLoading } = useVehicles();
   const [isEditingProfile, setIsEditingProfile] = useState(false);
   const [editedDisplayName, setEditedDisplayName] = useState('');
   const [editedNotificationEmail, setEditedNotificationEmail] = useState('');
@@ -277,6 +282,62 @@ export const SettingsPage: React.FC = () => {
           )}
         </Card>
 
+        {/* My Vehicles Section */}
+        <Card>
+          <Box sx={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', mb: 3 }}>
+            <Box sx={{ display: 'flex', alignItems: 'center', gap: 1 }}>
+              <DirectionsCarIcon color="primary" />
+              <Typography variant="h6" sx={{ fontWeight: 600 }}>
+                My Vehicles
+              </Typography>
+              {!vehiclesLoading && vehicles && (
+                <Typography variant="body2" color="text.secondary">
+                  ({vehicles.length})
+                </Typography>
+              )}
+            </Box>
+            <MuiButton
+              variant="contained"
+              size="small"
+              onClick={() => navigate('/garage')}
+              sx={{
+                backgroundColor: 'primary.main',
+                color: 'primary.contrastText',
+                '&:hover': {
+                  backgroundColor: 'primary.dark'
+                }
+              }}
+            >
+              Manage
+            </MuiButton>
+          </Box>
+
+          {vehiclesLoading ? (
+            <Box sx={{ display: 'flex', justifyContent: 'center', py: 3 }}>
+              <CircularProgress size={24} />
+            </Box>
+          ) : !vehicles?.length ? (
+            <Typography variant="body2" color="text.secondary" sx={{ py: 2 }}>
+              No vehicles registered. Add your first vehicle to get started.
+            </Typography>
+          ) : (
+            <List disablePadding>
+              {vehicles.map((vehicle, index) => (
+                <React.Fragment key={vehicle.id}>
+                  {index > 0 && <Divider />}
+                  <ListItem sx={{ py: 1.5 }}>
+                    <ListItemText
+                      primary={`${vehicle.year} ${vehicle.make} ${vehicle.model}`}
+                      secondary={vehicle.nickname || undefined}
+                      primaryTypographyProps={{ fontWeight: 500 }}
+                    />
+                  </ListItem>
+                </React.Fragment>
+              ))}
+            </List>
+          )}
+        </Card>
+
         {/* Notifications Section */}
         <Card>
           <Typography variant="h6" sx={{ fontWeight: 600, mb: 3 }}>

frontend/src/pages/admin/AdminUsersPage.tsx

@@ -10,6 +10,7 @@ import {
   Button,
   Chip,
   CircularProgress,
+  Collapse,
   Dialog,
   DialogActions,
   DialogContent,
@@ -44,6 +45,9 @@ import {
   Edit,
   Security,
   DeleteForever,
+  DirectionsCar,
+  KeyboardArrowDown,
+  KeyboardArrowUp,
 } from '@mui/icons-material';
 import { useAdminAccess } from '../../core/auth/useAdminAccess';
 import {
@@ -54,6 +58,8 @@ import {
   useUpdateUserProfile,
   usePromoteToAdmin,
   useHardDeleteUser,
+  useAdminStats,
+  useUserVehicles,
 } from '../../features/admin/hooks/useUsers';
 import {
   ManagedUser,
@@ -64,6 +70,58 @@ import { AdminSectionHeader } from '../../features/admin/components';
 
 const PAGE_SIZE_OPTIONS = [10, 20, 50, 100];
 
+// Expandable vehicle row component
+const UserVehiclesRow: React.FC<{ auth0Sub: string; isOpen: boolean }> = ({ auth0Sub, isOpen }) => {
+  const { data, isLoading, error } = useUserVehicles(auth0Sub);
+
+  if (!isOpen) return null;
+
+  return (
+    <TableRow>
+      <TableCell colSpan={9} sx={{ py: 0, bgcolor: 'action.hover' }}>
+        <Collapse in={isOpen} timeout="auto" unmountOnExit>
+          <Box sx={{ py: 2, px: 3 }}>
+            <Typography variant="subtitle2" sx={{ mb: 1, display: 'flex', alignItems: 'center', gap: 1 }}>
+              <DirectionsCar fontSize="small" />
+              Vehicles
+            </Typography>
+            {isLoading ? (
+              <CircularProgress size={20} />
+            ) : error ? (
+              <Typography variant="body2" color="error">
+                Failed to load vehicles
+              </Typography>
+            ) : !data?.vehicles?.length ? (
+              <Typography variant="body2" color="text.secondary">
+                No vehicles registered
+              </Typography>
+            ) : (
+              <Table size="small" sx={{ maxWidth: 500 }}>
+                <TableHead>
+                  <TableRow>
+                    <TableCell sx={{ fontWeight: 600 }}>Year</TableCell>
+                    <TableCell sx={{ fontWeight: 600 }}>Make</TableCell>
+                    <TableCell sx={{ fontWeight: 600 }}>Model</TableCell>
+                  </TableRow>
+                </TableHead>
+                <TableBody>
+                  {data.vehicles.map((vehicle, idx) => (
+                    <TableRow key={idx}>
+                      <TableCell>{vehicle.year}</TableCell>
+                      <TableCell>{vehicle.make}</TableCell>
+                      <TableCell>{vehicle.model}</TableCell>
+                    </TableRow>
+                  ))}
+                </TableBody>
+              </Table>
+            )}
+          </Box>
+        </Collapse>
+      </TableCell>
+    </TableRow>
+  );
+};
+
 export const AdminUsersPage: React.FC = () => {
   const { isAdmin, loading: adminLoading } = useAdminAccess();
 
@@ -110,6 +168,12 @@ export const AdminUsersPage: React.FC = () => {
   const [hardDeleteReason, setHardDeleteReason] = useState('');
   const [hardDeleteConfirmText, setHardDeleteConfirmText] = useState('');
 
+  // Expanded row state for vehicle list
+  const [expandedRow, setExpandedRow] = useState<string | null>(null);
+
+  // Admin stats query
+  const { data: statsData } = useAdminStats();
+
   // Handlers
   const handleSearch = useCallback(() => {
     setParams(prev => ({ ...prev, search: searchInput || undefined, page: 1 }));
@@ -319,7 +383,10 @@ export const AdminUsersPage: React.FC = () => {
     <Box sx={{ py: 2, display: 'flex', flexDirection: 'column', gap: 3 }}>
       <AdminSectionHeader
         title="User Management"
-        stats={[{ label: 'Total Users', value: total }]}
+        stats={[
+          { label: 'Total Users', value: statsData?.totalUsers ?? total },
+          { label: 'Total Vehicles', value: statsData?.totalVehicles ?? 0 },
+        ]}
       />
 
       {/* Filters Bar */}
@@ -429,55 +496,83 @@ export const AdminUsersPage: React.FC = () => {
                 </TableHead>
                 <TableBody>
                   {users.map((user) => (
-                    <TableRow
-                      key={user.auth0Sub}
-                      sx={{ opacity: user.deactivatedAt ? 0.6 : 1 }}
-                    >
-                      <TableCell>{user.email}</TableCell>
-                      <TableCell>{user.displayName || '-'}</TableCell>
-                      <TableCell>
-                        <FormControl size="small" sx={{ minWidth: 100 }}>
-                          <Select
-                            value={user.subscriptionTier}
-                            onChange={(e) =>
-                              handleTierChange(user.auth0Sub, e.target.value as SubscriptionTier)
-                            }
-                            disabled={!!user.deactivatedAt || updateTierMutation.isPending}
+                    <React.Fragment key={user.auth0Sub}>
+                      <TableRow
+                        sx={{
+                          opacity: user.deactivatedAt ? 0.6 : 1,
+                          '& > *': { borderBottom: expandedRow === user.auth0Sub ? 'unset' : undefined },
+                        }}
+                      >
+                        <TableCell>{user.email}</TableCell>
+                        <TableCell>{user.displayName || '-'}</TableCell>
+                        <TableCell>
+                          <FormControl size="small" sx={{ minWidth: 100 }}>
+                            <Select
+                              value={user.subscriptionTier}
+                              onChange={(e) =>
+                                handleTierChange(user.auth0Sub, e.target.value as SubscriptionTier)
+                              }
+                              disabled={!!user.deactivatedAt || updateTierMutation.isPending}
+                              size="small"
+                            >
+                              <MenuItem value="free">Free</MenuItem>
+                              <MenuItem value="pro">Pro</MenuItem>
+                              <MenuItem value="enterprise">Enterprise</MenuItem>
+                            </Select>
+                          </FormControl>
+                        </TableCell>
+                        <TableCell>
+                          <Box sx={{ display: 'flex', alignItems: 'center', gap: 0.5 }}>
+                            {user.vehicleCount > 0 && (
+                              <IconButton
+                                size="small"
+                                onClick={() => setExpandedRow(
+                                  expandedRow === user.auth0Sub ? null : user.auth0Sub
+                                )}
+                                aria-label="show vehicles"
+                                sx={{ minWidth: 44, minHeight: 44 }}
+                              >
+                                {expandedRow === user.auth0Sub ? (
+                                  <KeyboardArrowUp fontSize="small" />
+                                ) : (
+                                  <KeyboardArrowDown fontSize="small" />
+                                )}
+                              </IconButton>
+                            )}
+                            <Typography variant="body2">{user.vehicleCount}</Typography>
+                          </Box>
+                        </TableCell>
+                        <TableCell>
+                          <Chip
+                            label={user.deactivatedAt ? 'Deactivated' : 'Active'}
+                            color={user.deactivatedAt ? 'error' : 'success'}
                             size="small"
+                          />
+                        </TableCell>
+                        <TableCell>
+                          {user.isAdmin && (
+                            <Tooltip title={`Admin (${user.adminRole})`}>
+                              <AdminPanelSettings color="primary" />
+                            </Tooltip>
+                          )}
+                        </TableCell>
+                        <TableCell>
+                          {new Date(user.createdAt).toLocaleDateString()}
+                        </TableCell>
+                        <TableCell align="right">
+                          <IconButton
+                            size="small"
+                            onClick={(e) => handleMenuOpen(e, user)}
                           >
-                            <MenuItem value="free">Free</MenuItem>
-                            <MenuItem value="pro">Pro</MenuItem>
-                            <MenuItem value="enterprise">Enterprise</MenuItem>
-                          </Select>
-                        </FormControl>
-                      </TableCell>
-                      <TableCell>{user.vehicleCount}</TableCell>
-                      <TableCell>
-                        <Chip
-                          label={user.deactivatedAt ? 'Deactivated' : 'Active'}
-                          color={user.deactivatedAt ? 'error' : 'success'}
-                          size="small"
-                        />
-                      </TableCell>
-                      <TableCell>
-                        {user.isAdmin && (
-                          <Tooltip title={`Admin (${user.adminRole})`}>
-                            <AdminPanelSettings color="primary" />
-                          </Tooltip>
-                        )}
-                      </TableCell>
-                      <TableCell>
-                        {new Date(user.createdAt).toLocaleDateString()}
-                      </TableCell>
-                      <TableCell align="right">
-                        <IconButton
-                          size="small"
-                          onClick={(e) => handleMenuOpen(e, user)}
-                        >
-                          <MoreVert />
-                        </IconButton>
-                      </TableCell>
-                    </TableRow>
+                            <MoreVert />
+                          </IconButton>
+                        </TableCell>
+                      </TableRow>
+                      <UserVehiclesRow
+                        auth0Sub={user.auth0Sub}
+                        isOpen={expandedRow === user.auth0Sub}
+                      />
+                    </React.Fragment>
                   ))}
                 </TableBody>
               </Table>