feat: add Subscription section to Settings page (refs #55)

Added a Subscription section to the desktop Settings page that displays:
- Current subscription tier (Free/Pro/Enterprise)
- Status indicator for non-active subscriptions
- Manage button linking to the subscription management page
- Descriptive text based on current tier

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

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

frontend/src/pages/SettingsPage.tsx

@@ -11,6 +11,7 @@ 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 { useSubscription } from '../features/subscription/hooks/useSubscription';
 import { useTheme } from '../shared-minimal/theme/ThemeContext';
 import { DeleteAccountDialog } from '../features/settings/components/DeleteAccountDialog';
 import { PendingDeletionBanner } from '../features/settings/components/PendingDeletionBanner';
@@ -32,7 +33,8 @@ import {
   MenuItem,
   FormControl,
   TextField,
-  CircularProgress
+  CircularProgress,
+  Chip
 } from '@mui/material';
 import AccountCircleIcon from '@mui/icons-material/AccountCircle';
 import NotificationsIcon from '@mui/icons-material/Notifications';
@@ -41,6 +43,7 @@ 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 CreditCardIcon from '@mui/icons-material/CreditCard';
 import EditIcon from '@mui/icons-material/Edit';
 import SaveIcon from '@mui/icons-material/Save';
 import CancelIcon from '@mui/icons-material/Cancel';
@@ -62,6 +65,11 @@ export const SettingsPage: React.FC = () => {
 
   // Vehicles state (for My Vehicles section)
   const { data: vehicles, isLoading: vehiclesLoading } = useVehicles();
+
+  // Subscription state
+  const { data: subscriptionData, isLoading: subscriptionLoading } = useSubscription();
+  const subscription = subscriptionData?.data;
+
   const [isEditingProfile, setIsEditingProfile] = useState(false);
   const [editedDisplayName, setEditedDisplayName] = useState('');
   const [editedNotificationEmail, setEditedNotificationEmail] = useState('');
@@ -378,6 +386,65 @@ export const SettingsPage: React.FC = () => {
           )}
         </Card>
 
+        {/* Subscription Section */}
+        <Card>
+          <Box sx={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', mb: 3 }}>
+            <Box sx={{ display: 'flex', alignItems: 'center', gap: 1 }}>
+              <CreditCardIcon color="primary" />
+              <Typography variant="h6" sx={{ fontWeight: 600 }}>
+                Subscription
+              </Typography>
+            </Box>
+            <MuiButton
+              variant="contained"
+              size="small"
+              onClick={() => navigate('/garage/settings/subscription')}
+              sx={{
+                backgroundColor: 'primary.main',
+                color: 'primary.contrastText',
+                '&:hover': {
+                  backgroundColor: 'primary.dark'
+                }
+              }}
+            >
+              Manage
+            </MuiButton>
+          </Box>
+
+          {subscriptionLoading ? (
+            <Box sx={{ display: 'flex', justifyContent: 'center', py: 3 }}>
+              <CircularProgress size={24} />
+            </Box>
+          ) : (
+            <Box sx={{ display: 'flex', flexDirection: 'column', gap: 2 }}>
+              <Box sx={{ display: 'flex', alignItems: 'center', gap: 2 }}>
+                <Typography variant="body1" sx={{ fontWeight: 500 }}>
+                  Current Plan:
+                </Typography>
+                <Chip
+                  label={(subscription?.tier || 'free').toUpperCase()}
+                  color="primary"
+                  size="small"
+                />
+                {subscription?.status && subscription.status !== 'active' && (
+                  <Chip
+                    label={subscription.status.replace('_', ' ')}
+                    color={subscription.status === 'past_due' ? 'warning' : 'error'}
+                    size="small"
+                  />
+                )}
+              </Box>
+              <Typography variant="body2" color="text.secondary">
+                {subscription?.tier === 'free'
+                  ? 'Upgrade to Pro or Enterprise for more features and vehicle slots.'
+                  : subscription?.tier === 'pro'
+                  ? 'Pro plan with up to 5 vehicles and full features.'
+                  : 'Enterprise plan with unlimited vehicles and all features.'}
+              </Typography>
+            </Box>
+          )}
+        </Card>
+
         {/* Notifications Section */}
         <Card>
           <Typography variant="h6" sx={{ fontWeight: 600, mb: 3 }}>