Finish the NestJS migration — drop the legacy Express app

NestJS now serves the whole surface: every /api domain plus the platform
routes (uploads, /mcp, the OAuth/MCP SDK + /.well-known metadata and the
production SPA fallback). Removed server/src/app.ts, all of
server/src/routes/* and the strangler dispatcher; index.ts and the
integration suite share a single buildApp() bootstrap so prod and tests
can't drift.

- Platform/transport routes extracted to nest/platform/platform.routes.ts
  and mounted before app.init() — Nest's router answers an unmatched
  request with a 404, so a route registered after init is never reached.
  The SPA fallback is a NotFoundException filter and the catch-all uses a
  RegExp (Express 5's path-to-regexp rejects a bare '*').
- New modules: memories (/api/integrations/memories — the Journey
  gallery's Immich/Synology proxy), addons (GET /api/addons) and the
  cross-trip GET /api/reservations/upcoming.
- TrekExceptionFilter reproduces the old multer / err.statusCode handling
  so upload rejections keep their 400/413 { error } body and non-ASCII
  filenames survive (defParamCharset).
- addTripToJourney and the MCP get_journey_share_link tool gained the
  trip-access check they were missing.
- Re-pointed the 34 integration tests + the websocket test onto the Nest
  app; removed the now-meaningless Express-vs-Nest parity tests and a few
  orphaned client components.

server/tests/unit/mcp/tools-prompts.test.ts

@@ -71,8 +71,10 @@ beforeEach(() => {
   isAddonEnabledMock.mockReturnValue(true);
 
   // Default mock: returns a trip-summary-shaped value from the real in-memory DB
-  // so that the trip title / existence match what tests insert, but budget/packing
-  // are arrays (as prompts.ts expects), not the object shape getTripSummary now returns.
+  // so the trip title / existence match what tests insert. `budget` mirrors the
+  // real getTripSummary object shape ({ items, total, ... }) that prompts.ts reads
+  // via budget.items/budget.total; packing stays an array (the packing prompt
+  // tolerates it).
   mockGetTripSummary.mockImplementation((tripId: any) => {
     const trip = testDb.prepare('SELECT * FROM trips WHERE id = ?').get(tripId) as any;
     if (!trip) return null;
@@ -87,8 +89,13 @@ beforeEach(() => {
       trip,
       days: [],
       members,
-      budget: budgetRows,   // array shape expected by prompts.ts
-      packing: packingRows, // array shape expected by prompts.ts
+      budget: {
+        items: budgetRows,
+        item_count: budgetRows.length,
+        total: budgetRows.reduce((sum, i) => sum + (i.total_price || 0), 0),
+        currency: trip.currency,
+      },
+      packing: packingRows, // array shape; packing prompt tolerates it
       reservations: [],
       collabNotes: [],
     };