feat: add TCO display component (refs #15)

- Create TCODisplay component showing lifetime cost and cost per distance
- Display cost breakdown (purchase, insurance, registration, fuel, maintenance)
- Integrate into VehicleDetailPage right-justified next to vehicle details
- Responsive layout: stacks vertically on mobile, side-by-side on desktop
- Only shows when tcoEnabled is true

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

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

frontend/src/features/vehicles/components/TCODisplay.tsx

@@ -0,0 +1,134 @@
+/**
+ * @ai-summary TCO (Total Cost of Ownership) display component
+ * Right-justified display showing lifetime cost and cost per mile/km
+ */
+
+import React, { useEffect, useState } from 'react';
+import { TCOResponse } from '../types/vehicles.types';
+import { vehiclesApi } from '../api/vehicles.api';
+
+interface TCODisplayProps {
+  vehicleId: string;
+  tcoEnabled?: boolean;
+}
+
+// Currency symbol mapping
+const CURRENCY_SYMBOLS: Record<string, string> = {
+  USD: '$',
+  EUR: '€',
+  GBP: '£',
+  CAD: 'CA$',
+  AUD: 'A$',
+};
+
+export const TCODisplay: React.FC<TCODisplayProps> = ({ vehicleId, tcoEnabled }) => {
+  const [tco, setTco] = useState<TCOResponse | null>(null);
+  const [isLoading, setIsLoading] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+
+  useEffect(() => {
+    if (!tcoEnabled) {
+      setTco(null);
+      return;
+    }
+
+    const fetchTCO = async () => {
+      setIsLoading(true);
+      setError(null);
+      try {
+        const data = await vehiclesApi.getTCO(vehicleId);
+        setTco(data);
+      } catch (err: any) {
+        console.error('Failed to fetch TCO:', err);
+        setError('Unable to load TCO data');
+      } finally {
+        setIsLoading(false);
+      }
+    };
+
+    fetchTCO();
+  }, [vehicleId, tcoEnabled]);
+
+  // Don't render if TCO is disabled
+  if (!tcoEnabled) {
+    return null;
+  }
+
+  // Loading state
+  if (isLoading) {
+    return (
+      <div className="text-right animate-pulse" role="region" aria-label="Total Cost of Ownership">
+        <div className="h-8 bg-gray-200 dark:bg-silverstone rounded w-32 ml-auto mb-1"></div>
+        <div className="h-4 bg-gray-200 dark:bg-silverstone rounded w-24 ml-auto mb-2"></div>
+        <div className="h-6 bg-gray-200 dark:bg-silverstone rounded w-20 ml-auto mb-1"></div>
+        <div className="h-4 bg-gray-200 dark:bg-silverstone rounded w-24 ml-auto"></div>
+      </div>
+    );
+  }
+
+  // Error state
+  if (error) {
+    return (
+      <div className="text-right text-sm text-gray-500 dark:text-titanio" role="region" aria-label="Total Cost of Ownership">
+        <span>{error}</span>
+      </div>
+    );
+  }
+
+  // No data
+  if (!tco) {
+    return null;
+  }
+
+  const currencySymbol = CURRENCY_SYMBOLS[tco.currencyCode] || tco.currencyCode;
+
+  // Format currency with proper separators
+  const formatCurrency = (value: number): string => {
+    return value.toLocaleString(undefined, {
+      minimumFractionDigits: 2,
+      maximumFractionDigits: 2,
+    });
+  };
+
+  return (
+    <div className="text-right" role="region" aria-label="Total Cost of Ownership">
+      <div className="text-2xl font-bold text-gray-900 dark:text-avus">
+        {currencySymbol}{formatCurrency(tco.lifetimeTotal)}
+      </div>
+      <div className="text-sm text-gray-500 dark:text-titanio mb-2">
+        Lifetime Total
+      </div>
+      {tco.costPerDistance > 0 && (
+        <>
+          <div className="text-lg text-gray-700 dark:text-canna">
+            {currencySymbol}{formatCurrency(tco.costPerDistance)}/{tco.distanceUnit}
+          </div>
+          <div className="text-sm text-gray-500 dark:text-titanio">
+            Cost per {tco.distanceUnit}
+          </div>
+        </>
+      )}
+
+      {/* Cost breakdown tooltip/details */}
+      <div className="mt-4 pt-4 border-t border-gray-200 dark:border-silverstone">
+        <div className="text-xs text-gray-500 dark:text-titanio text-right space-y-1">
+          {tco.purchasePrice > 0 && (
+            <div>Purchase: {currencySymbol}{formatCurrency(tco.purchasePrice)}</div>
+          )}
+          {tco.insuranceCosts > 0 && (
+            <div>Insurance: {currencySymbol}{formatCurrency(tco.insuranceCosts)}</div>
+          )}
+          {tco.registrationCosts > 0 && (
+            <div>Registration: {currencySymbol}{formatCurrency(tco.registrationCosts)}</div>
+          )}
+          {tco.fuelCosts > 0 && (
+            <div>Fuel: {currencySymbol}{formatCurrency(tco.fuelCosts)}</div>
+          )}
+          {tco.maintenanceCosts > 0 && (
+            <div>Maintenance: {currencySymbol}{formatCurrency(tco.maintenanceCosts)}</div>
+          )}
+        </div>
+      </div>
+    </div>
+  );
+};

frontend/src/features/vehicles/pages/VehicleDetailPage.tsx

@@ -15,6 +15,7 @@ import { vehiclesApi } from '../api/vehicles.api';
 import { Card } from '../../../shared-minimal/components/Card';
 import { VehicleForm } from '../components/VehicleForm';
 import { VehicleImage } from '../components/VehicleImage';
+import { TCODisplay } from '../components/TCODisplay';
 import { useFuelLogs } from '../../fuel-logs/hooks/useFuelLogs';
 import { FuelLogResponse, UpdateFuelLogRequest } from '../../fuel-logs/types/fuel-logs.types';
 import { FuelLogEditDialog } from '../../fuel-logs/components/FuelLogEditDialog';
@@ -300,8 +301,8 @@ export const VehicleDetailPage: React.FC = () => {
       </Box>
 
       <Card>
-        <Box sx={{ display: 'flex', gap: 3, mb: 3 }}>
-          <Box sx={{ width: 200, flexShrink: 0 }}>
+        <Box sx={{ display: 'flex', gap: 3, mb: 3, flexWrap: { xs: 'wrap', md: 'nowrap' } }}>
+          <Box sx={{ width: { xs: '100%', sm: 200 }, flexShrink: 0 }}>
             <VehicleImage vehicle={vehicle} height={150} />
           </Box>
           <Box sx={{ flex: 1 }}>
@@ -318,6 +319,14 @@ export const VehicleDetailPage: React.FC = () => {
               </Typography>
             )}
           </Box>
+          {/* TCO Display - right-justified */}
+          <Box sx={{
+            width: { xs: '100%', md: 'auto' },
+            minWidth: { md: 200 },
+            mt: { xs: 2, md: 0 }
+          }}>
+            <TCODisplay vehicleId={vehicle.id} tcoEnabled={vehicle.tcoEnabled} />
+          </Box>
         </Box>
 
         <form className="space-y-4">