test: Phase 0 测试基础设施 — TestApp + MSW + 覆盖率工具 + CI

- TestApp struct 封装 TestDb + HealthState + tenant_id/operator_id
- TestFixture 工厂方法: create_patient/create_doctor/create_schedule/create_appointment
- 前端 MSW v2 handlers (auth) + server setup + vitest 集成
- vitest coverage v8 配置 + test:coverage script
- GitHub Actions CI: backend (check + test + clippy) + frontend (tsc + test + build)

apps/web/src/test/mocks/handlers.ts

@@ -0,0 +1,30 @@
+import { http, HttpResponse } from 'msw';
+
+const TOKEN_EXPIRES = 3600;
+
+export const authHandlers = [
+  http.post('/api/v1/auth/login', () =>
+    HttpResponse.json({
+      success: true,
+      data: {
+        access_token: 'test-access-token',
+        refresh_token: 'test-refresh-token',
+        expires_in: TOKEN_EXPIRES,
+        user: { id: 'test-user-id', username: 'admin', tenant_id: 'test-tenant-id' },
+      },
+    }),
+  ),
+
+  http.post('/api/v1/auth/refresh', () =>
+    HttpResponse.json({
+      success: true,
+      data: {
+        access_token: 'test-access-token-refreshed',
+        refresh_token: 'test-refresh-token-refreshed',
+        expires_in: TOKEN_EXPIRES,
+      },
+    }),
+  ),
+];
+
+export const handlers = [...authHandlers];