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.

client/src/api/client.ts

@@ -1,4 +1,5 @@
 import axios, { AxiosInstance } from 'axios'
+import type { WeatherResult } from '@trek/shared'
 import { getSocketId } from './websocket'
 import { isReachable, probeNow } from '../sync/connectivity'
 import en from '../i18n/translations/en'
@@ -501,8 +502,8 @@ export const reservationsApi = {
 }
 
 export const weatherApi = {
-  get: (lat: number, lng: number, date: string) => apiClient.get('/weather', { params: { lat, lng, date } }).then(r => r.data),
-  getDetailed: (lat: number, lng: number, date: string, lang?: string) => apiClient.get('/weather/detailed', { params: { lat, lng, date, lang } }).then(r => r.data),
+  get: (lat: number, lng: number, date: string): Promise<WeatherResult> => apiClient.get('/weather', { params: { lat, lng, date } }).then(r => r.data),
+  getDetailed: (lat: number, lng: number, date: string, lang?: string): Promise<WeatherResult> => apiClient.get('/weather/detailed', { params: { lat, lng, date, lang } }).then(r => r.data),
 }
 
 export const configApi = {