feat: add ownership-costs feature capsule (refs #15)

- Create ownership_costs table for recurring vehicle costs
- Add backend feature capsule with types, repository, service, routes
- Update TCO calculation to use ownership_costs (with fallback to legacy vehicle fields)
- Add taxCosts and otherCosts to TCO response
- Create frontend ownership-costs feature with form, list, API, hooks
- Update TCODisplay to show all cost types

This implements a more flexible approach to tracking recurring ownership costs
(insurance, registration, tax, other) with explicit date ranges and optional
document association.

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

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

backend/src/features/ownership-costs/api/ownership-costs.routes.ts

@@ -0,0 +1,56 @@
+/**
+ * @ai-summary Fastify routes for ownership costs API
+ * @ai-context Route definitions with Fastify plugin pattern and authentication
+ */
+
+import { FastifyInstance, FastifyPluginOptions } from 'fastify';
+import { FastifyPluginAsync } from 'fastify';
+import { OwnershipCostsController } from './ownership-costs.controller';
+
+export const ownershipCostsRoutes: FastifyPluginAsync = async (
+  fastify: FastifyInstance,
+  _opts: FastifyPluginOptions
+) => {
+  const controller = new OwnershipCostsController();
+
+  // POST /api/ownership-costs - Create new ownership cost
+  fastify.post('/ownership-costs', {
+    preHandler: [fastify.authenticate],
+    handler: controller.create.bind(controller)
+  });
+
+  // GET /api/ownership-costs/:id - Get specific ownership cost
+  fastify.get('/ownership-costs/:id', {
+    preHandler: [fastify.authenticate],
+    handler: controller.getById.bind(controller)
+  });
+
+  // PUT /api/ownership-costs/:id - Update ownership cost
+  fastify.put('/ownership-costs/:id', {
+    preHandler: [fastify.authenticate],
+    handler: controller.update.bind(controller)
+  });
+
+  // DELETE /api/ownership-costs/:id - Delete ownership cost
+  fastify.delete('/ownership-costs/:id', {
+    preHandler: [fastify.authenticate],
+    handler: controller.delete.bind(controller)
+  });
+
+  // GET /api/ownership-costs/vehicle/:vehicleId - Get costs for a vehicle
+  fastify.get('/ownership-costs/vehicle/:vehicleId', {
+    preHandler: [fastify.authenticate],
+    handler: controller.getByVehicle.bind(controller)
+  });
+
+  // GET /api/ownership-costs/vehicle/:vehicleId/stats - Get aggregated cost stats
+  fastify.get('/ownership-costs/vehicle/:vehicleId/stats', {
+    preHandler: [fastify.authenticate],
+    handler: controller.getVehicleStats.bind(controller)
+  });
+};
+
+// For backward compatibility during migration
+export function registerOwnershipCostsRoutes() {
+  throw new Error('registerOwnershipCostsRoutes is deprecated - use ownershipCostsRoutes Fastify plugin instead');
+}