test(integration): Postgres testcontainers + 4 critical-path tests (rate-limit race, idempotency, cascade, session) (#137)

* test(integration): Postgres testcontainers + 4 critical-path tests

Adds an integration test suite that runs against a real Postgres booted
in-process via testcontainers. Lives under tests/integration/, runs via
`pnpm test:integration`, and is excluded from the default `pnpm test`
loop so the 477-test unit suite stays fast (~1.2s).

Covers four regression-prone behaviours that pure unit tests cannot
validate against a mocked client:

- rate-limit.test.ts — atomic UPSERT under concurrency (5/6 allowed)
  and window-reset semantics for src/lib/rate-limit.ts
- idempotency-replay.test.ts — cached replay with X-Idempotent-Replay,
  expired-row purge, and the do-not-cache contract for 401/403/408/429/5xx
  on top of src/lib/idempotency.ts
- cascade-delete.test.ts — GDPR Art. 17 erasure: user.delete wipes
  every onDelete:Cascade table and SetNulls AuditLog/Feedback
- auth-flow.test.ts — createSession/getSession round-trip plus
  expired-session purge for src/lib/auth/session.ts

Adds .github/workflows/integration.yml triggering on pull_request and
push to main. Local Docker is not running in this worktree environment;
the suite was verified by collecting all 10 tests via `vitest list` and
will execute in CI.

Co-Authored-By: Marc-André Bombeck <mbombeck@gmail.com>
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* test(integration): rebase onto v1.4 + exclude live agent worktrees from default test scope

Rebase brings PR #137's testcontainers infrastructure on top of the
user-locale migration drift fix landed in #140 — the integration suite
should now bootstrap a fresh Postgres container with all 25 migrations
applied cleanly.

vitest.config.mts also gains a `.claude/worktrees/**` exclude so live
agent worktrees (which mirror `src/` while their parent agents are
running) don't double-execute the project's tests against possibly-stale
copies.

* test(integration): boot one Postgres container per run via vitest globalSetup

The first iteration of the testcontainers suite started/stopped a
fresh container in each test file's beforeAll/afterAll. That works
in isolation but breaks when files share a worker (`pool: forks`,
`fileParallelism: false`, `isolate: false`):

  1. Test file A boots container 1, sets DATABASE_URL.
  2. The application's Prisma singleton in src/lib/db.ts is built
     when test code dynamic-imports @/lib/auth/session — it captures
     container 1's URL.
  3. afterAll stops container 1.
  4. Test file B boots container 2, sets DATABASE_URL to a new port.
  5. Test file B imports application code that resolves to the same
     singleton — still pointing at the dead container 1. Queries fail
     with a generic PrismaClientKnownRequestError.

Fix: move the container lifecycle to vitest's globalSetup. One
container, booted once, torn down at the end of the run. Tests still
get isolation because beforeEach truncates every personal-data table
in dependency-safe CASCADE order.

  - tests/integration/global-setup.ts boots postgres:16-alpine,
    runs `pnpm db:migrate:deploy`, exports a teardown for end-of-run.
  - tests/integration/setup.ts now exports getPrismaClient() (which
    delegates to the application singleton) and truncateAllTables().
    No more startTestDb / stopTestDb.
  - All four test files lose their beforeAll/afterAll boilerplate.
  - vitest.integration.config.mts wires the new globalSetup.
  - truncate list adds refresh_tokens (added in 0025_refresh_tokens).

Result: pnpm test:integration → 10/10 pass in 3.9s (was 6/10 with
4 cross-file failures). pnpm test → 658/658 unchanged.

Co-Authored-By: Marc-André Bombeck <mbombeck@gmail.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/integration.yml

@@ -0,0 +1,34 @@
+name: Integration tests
+
+on:
+  pull_request:
+    branches: [main]
+  push:
+    branches: [main]
+
+jobs:
+  integration:
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: pnpm/action-setup@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: pnpm
+
+      - run: pnpm install --frozen-lockfile
+
+      - run: pnpm db:generate
+
+      - run: pnpm test:integration
+        env:
+          # The integration suite boots a Postgres testcontainer and points
+          # Prisma at it via DATABASE_URL set inside `tests/integration/setup.ts`.
+          # These env vars satisfy code paths that read them at module load.
+          API_TOKEN_HMAC_KEY: integration-tests-do-not-use-in-prod
+          ENCRYPTION_KEY: 0000000000000000000000000000000000000000000000000000000000000000
+          SESSION_SECRET: integration-tests