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/src/nest/app.module.ts

@@ -3,6 +3,7 @@ import { APP_FILTER } from '@nestjs/core';
 import { DatabaseModule } from './database/database.module';
 import { HealthController } from './health/health.controller';
 import { HealthService } from './health/health.service';
+import { WeatherModule } from './weather/weather.module';
 import { TrekExceptionFilter } from './common/trek-exception.filter';
 
 /**
@@ -10,7 +11,7 @@ import { TrekExceptionFilter } from './common/trek-exception.filter';
  * (weather, notifications, ...) get registered here as they are migrated.
  */
 @Module({
-  imports: [DatabaseModule],
+  imports: [DatabaseModule, WeatherModule],
   controllers: [HealthController],
   providers: [
     HealthService,