fix: migrate E2E tests from SQLite to Postgres

- Rewrite e2e/seed.ts to use postgres driver instead of bun:sqlite
- Add userId to all seeded entities (multi-user schema)
- Add Postgres service container to CI E2E job
- Remove DATABASE_PATH from test server start script
- Re-enable E2E job in CI

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -30,11 +30,24 @@ jobs:
         run: bun run build
 
   e2e:
-    if: false  # Disabled: E2E requires Postgres (Phase 14) — SQLite schema diverged at v2.0
     needs: ci
     runs-on: docker
     container:
       image: mcr.microsoft.com/playwright:v1.59.1-noble
+    services:
+      postgres:
+        image: postgres:16-alpine
+        env:
+          POSTGRES_USER: gearbox
+          POSTGRES_PASSWORD: gearbox
+          POSTGRES_DB: gearbox
+        options: >-
+          --health-cmd "pg_isready -U gearbox"
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
+    env:
+      DATABASE_URL: postgresql://gearbox:gearbox@postgres:5432/gearbox
     steps:
       - name: Checkout
         uses: actions/checkout@v4