feat(01-01): Drizzle schema + DB client + /health slice (GREEN)

- src/db/schema.ts: users, memberCredentials, calendars, calendarEvents tables
  - users: composite unique on oidc_iss+oidc_sub (D-10 identity)
  - calendar_events: separate dtstart_utc (TIMESTAMP) and dtstart_date (DATE) + allDay boolean (D-13)
- src/db/client.ts: drizzle(mysql2 pool) singleton export `db`
- drizzle.config.ts: dialect mysql, schema → migrations, dbCredentials from env
- src/routes/health.ts: GET / with real SELECT 1 DB round-trip, 200 or 503
- src/index.ts: Hono app with /health mounted before auth, serveStatic for PWA
- tests/health.test.ts: 2 tests pass (mocked DB); TDD GREEN gate
- apps/pwa/src/App.tsx: React shell fetching /health via TanStack Query

apps/api/tests/health.test.ts

@@ -1,47 +1,35 @@
 /**
  * GET /health — end-to-end skeleton test
  *
- * TDD RED: Tests written before implementation.
- * These will fail until Task 2 creates apps/api/src/routes/health.ts
- * and apps/api/src/index.ts.
- *
- * Behavior (from plan):
- *   - GET /health returns 200 with { ok: true, db: "up" } after a real DB round-trip
+ * Behavior:
+ *   - GET /health returns 200 with { ok: true, db: "up" } after DB round-trip succeeds
  *   - GET /health returns 503 if the DB round-trip throws
  */
 
-import { describe, it, expect, vi, beforeEach } from 'vitest'
+import { describe, it, expect, vi } from 'vitest'
 
-// We test the health route by importing the Hono app and calling it directly
-// (no real DB needed — we mock the db module)
+// vi.mock is hoisted to the top of the module by Vitest — defining it here is correct.
+// The factory is called before any test runs.
+vi.mock('../src/db/client.js', () => ({
+  db: {
+    execute: vi.fn().mockResolvedValue([[{ '1': 1 }]]),
+  },
+}))
 
 describe('GET /health', () => {
-  beforeEach(() => {
-    vi.resetModules()
-  })
-
   it('returns 200 with { ok: true, db: "up" } when DB round-trip succeeds', async () => {
-    // Mock the db module so no real MariaDB is needed
-    vi.mock('../src/db/client.js', () => ({
-      db: {
-        execute: vi.fn().mockResolvedValue([[]]),
-      },
-    }))
-
     const { app } = await import('../src/index.js')
     const res = await app.request('/health')
     expect(res.status).toBe(200)
-    const body = await res.json()
+    const body = await res.json() as { ok: boolean; db: string }
     expect(body.ok).toBe(true)
     expect(body.db).toBe('up')
   })
 
   it('returns 503 when DB round-trip throws', async () => {
-    vi.mock('../src/db/client.js', () => ({
-      db: {
-        execute: vi.fn().mockRejectedValue(new Error('DB connection failed')),
-      },
-    }))
+    const { db } = await import('../src/db/client.js')
+    // Temporarily override execute to throw
+    vi.mocked(db.execute).mockRejectedValueOnce(new Error('DB connection failed'))
 
     const { app } = await import('../src/index.js')
     const res = await app.request('/health')