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/tests/unit/nest/database-service.test.ts

@@ -0,0 +1,36 @@
+/**
+ * DatabaseService — the shared better-sqlite3 provider (F3). Exercises every
+ * helper against the real connection so the typed query surface is covered.
+ */
+import { describe, it, expect } from 'vitest';
+import { DatabaseService } from '../../../src/nest/database/database.service';
+
+describe('DatabaseService (typed query helpers)', () => {
+  const svc = new DatabaseService();
+
+  it('exposes the shared connection', () => {
+    expect(typeof svc.connection.prepare).toBe('function');
+  });
+
+  it('prepare + get + all return rows from the live connection', () => {
+    expect(svc.prepare('SELECT 1 AS one').get()).toEqual({ one: 1 });
+    expect(svc.get('SELECT 2 AS two')).toEqual({ two: 2 });
+    expect(svc.all('SELECT 3 AS three')).toEqual([{ three: 3 }]);
+  });
+
+  it('run + transaction operate on a scratch table', () => {
+    svc.run('CREATE TEMP TABLE IF NOT EXISTS _dbsvc_test (n INTEGER)');
+    svc.run('DELETE FROM _dbsvc_test');
+
+    const info = svc.run('INSERT INTO _dbsvc_test (n) VALUES (?)', 41);
+    expect(info.changes).toBe(1);
+
+    const total = svc.transaction((conn) => {
+      conn.prepare('INSERT INTO _dbsvc_test (n) VALUES (?)').run(1);
+      return conn.prepare('SELECT SUM(n) AS s FROM _dbsvc_test').get() as { s: number };
+    });
+    expect(total.s).toBe(42);
+
+    svc.run('DROP TABLE _dbsvc_test');
+  });
+});

server/tests/unit/nest/strangler.test.ts

@@ -8,9 +8,9 @@ describe('strangler toggle', () => {
     else process.env.NEST_PREFIXES = original;
   });
 
-  it('defaults to /api/_nest when NEST_PREFIXES is unset', () => {
+  it('defaults to the migrated prefixes (/api/_nest + /api/weather) when NEST_PREFIXES is unset', () => {
     delete process.env.NEST_PREFIXES;
-    expect(getNestPrefixes()).toEqual(['/api/_nest']);
+    expect(getNestPrefixes()).toEqual(['/api/_nest', '/api/weather']);
   });
 
   it('parses NEST_PREFIXES (comma-separated, trimmed)', () => {

server/tests/unit/nest/weather.controller.test.ts

@@ -0,0 +1,93 @@
+import { describe, it, expect, vi } from 'vitest';
+import { HttpException } from '@nestjs/common';
+import { WeatherController } from '../../../src/nest/weather/weather.controller';
+import { ApiError } from '../../../src/services/weatherService';
+import type { WeatherService } from '../../../src/nest/weather/weather.service';
+
+function makeController(svc: Partial<WeatherService>) {
+  return new WeatherController(svc as WeatherService);
+}
+
+/** Run `fn`, expecting it to throw an HttpException; return its { status, body }. */
+async function thrown(fn: () => Promise<unknown>): Promise<{ status: number; body: unknown }> {
+  try {
+    await fn();
+  } catch (err) {
+    expect(err).toBeInstanceOf(HttpException);
+    const e = err as HttpException;
+    return { status: e.getStatus(), body: e.getResponse() };
+  }
+  throw new Error('expected the handler to throw');
+}
+
+describe('WeatherController (parity with the legacy /api/weather route)', () => {
+  const sample = { temp: 21, main: 'Clear', description: 'Klar', type: 'current' };
+
+  describe('GET /api/weather', () => {
+    it('400 { error } with the exact legacy message when lat/lng missing', async () => {
+      const c = makeController({ get: vi.fn() });
+      expect(await thrown(() => c.getWeather(undefined, '13.4'))).toEqual({
+        status: 400,
+        body: { error: 'Latitude and longitude are required' },
+      });
+    });
+
+    it('returns the service result and defaults lang to "de" when absent', async () => {
+      const get = vi.fn().mockResolvedValue(sample);
+      const c = makeController({ get });
+      const res = await c.getWeather('52.5', '13.4', undefined, undefined);
+      expect(res).toEqual(sample);
+      expect(get).toHaveBeenCalledWith('52.5', '13.4', undefined, 'de');
+    });
+
+    it('passes an explicit lang and date through unchanged', async () => {
+      const get = vi.fn().mockResolvedValue(sample);
+      const c = makeController({ get });
+      await c.getWeather('1', '2', '2026-07-01', 'en');
+      expect(get).toHaveBeenCalledWith('1', '2', '2026-07-01', 'en');
+    });
+
+    it('maps an ApiError to its status + { error: message }', async () => {
+      const c = makeController({ get: vi.fn().mockRejectedValue(new ApiError(404, 'Open-Meteo API error')) });
+      expect(await thrown(() => c.getWeather('1', '2'))).toEqual({
+        status: 404,
+        body: { error: 'Open-Meteo API error' },
+      });
+    });
+
+    it('maps an unexpected error to the exact legacy 500 body', async () => {
+      vi.spyOn(console, 'error').mockImplementation(() => {});
+      const c = makeController({ get: vi.fn().mockRejectedValue(new Error('boom')) });
+      expect(await thrown(() => c.getWeather('1', '2'))).toEqual({
+        status: 500,
+        body: { error: 'Error fetching weather data' },
+      });
+    });
+  });
+
+  describe('GET /api/weather/detailed', () => {
+    it('400 { error } with the exact legacy message when date missing', async () => {
+      const c = makeController({ getDetailed: vi.fn() });
+      expect(await thrown(() => c.getDetailed('1', '2', undefined))).toEqual({
+        status: 400,
+        body: { error: 'Latitude, longitude, and date are required' },
+      });
+    });
+
+    it('returns the detailed result and defaults lang to "de"', async () => {
+      const getDetailed = vi.fn().mockResolvedValue(sample);
+      const c = makeController({ getDetailed });
+      await c.getDetailed('1', '2', '2026-07-01', undefined);
+      expect(getDetailed).toHaveBeenCalledWith('1', '2', '2026-07-01', 'de');
+    });
+
+    it('maps an unexpected error to the exact detailed 500 body', async () => {
+      vi.spyOn(console, 'error').mockImplementation(() => {});
+      const c = makeController({ getDetailed: vi.fn().mockRejectedValue(new Error('boom')) });
+      expect(await thrown(() => c.getDetailed('1', '2', '2026-07-01'))).toEqual({
+        status: 500,
+        body: { error: 'Error fetching detailed weather data' },
+      });
+    });
+  });
+});