feat(weather): migrate /api/weather to the NestJS pilot module (L1) (#1053)

First strangler migration (L1): /api/weather is served by a NestJS module.

- @trek/shared/weather Zod contract; Nest controller byte-identical to the legacy Express route (paths, query params, status codes, { error } bodies, lang default, ApiError/500 passthrough). Service reuses getWeather/getDetailedWeather (+ shared cache; MCP tools unchanged).
- Strangler routes /api/weather to Nest by default; the legacy Express route + its migration-time parity test were decommissioned in this PR.
- Frontend (FE2): weatherApi typed against the @trek/shared WeatherResult contract.
- Harness: reusable Nest-vs-Express parity harness, e2e harness (temp SQLite + seed/cookie helpers, real JwtAuthGuard), src/nest coverage gate raised to >=80%, src/nest test guide.
- Verified end-to-end on a prod mirror (dev1): 401/400/200 via Nest with real Open-Meteo data, Express route gone.

server/package.json

@@ -13,6 +13,8 @@
     "test:unit": "vitest run tests/unit",
     "test:integration": "vitest run tests/integration",
     "test:ws": "vitest run tests/websocket",
+    "test:parity": "vitest run tests/parity",
+    "test:e2e": "vitest run tests/e2e",
     "test:coverage": "vitest run --coverage"
   },
   "dependencies": {