fix(ci): set DATABASE_TEST_URL + downgrade upload-artifact to v3 (Gitea Actions)

Two CI-config issues blocking the gate from going green:

1. **Backend tests connect to localhost instead of postgres service.**
   conftest.py reads DATABASE_TEST_URL only — DATABASE_URL is intentionally
   not consulted (per dab740d's test-DB-isolation hardening — running
   pytest with DATABASE_URL set previously dropped the dev DB schema).
   The CI workflow only sets DATABASE_URL, so conftest falls back to its
   localhost default and every fixture-setup fails with
   `OSError: Connect call failed ('127.0.0.1', 5432)` — observed as 638
   errors on the latest main run.

   Add DATABASE_TEST_URL pointing at the postgres service container.
   Same connection string as DATABASE_URL — the test DB and the app DB
   are the same physical postgres in CI; conftest's safety assertion is
   satisfied by the URL containing "test".

2. **Frontend artifact upload fails on Gitea Actions runner.**
   actions/upload-artifact@v4 (and v5) are not supported on Gitea
   Actions / GHES — the runner returns
   `GHESNotSupportedError: ... not currently supported on GHES`. Lint
   itself is now passing (0 errors after PR #149); the job exits 1 only
   because the upload step then fails.

   Pin upload-artifact + download-artifact to v3, the latest version
   compatible with Gitea Actions until they ship v4 support.

After this lands, both backend and frontend CI gates should turn
green — at which point we can also add backend to the required status
checks on main.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -28,6 +28,12 @@ jobs:
     env:
       DATABASE_URL: postgresql+asyncpg://postgres:postgres@postgres:5432/resolutionflow_test
       DATABASE_URL_SYNC: postgresql://postgres:postgres@postgres:5432/resolutionflow_test
+      # conftest.py reads DATABASE_TEST_URL only (DATABASE_URL is intentionally
+      # not consulted after the dab740d test-isolation hardening). The CI test
+      # DB is the same postgres service, so point DATABASE_TEST_URL at it
+      # explicitly — without this, conftest falls back to localhost:5432 and
+      # all tests fail at fixture setup with "connection refused".
+      DATABASE_TEST_URL: postgresql+asyncpg://postgres:postgres@postgres:5432/resolutionflow_test
       SECRET_KEY: ci-test-secret-key-not-for-production
       DEBUG: "true"
       APP_NAME: ResolutionFlow
@@ -88,7 +94,7 @@ jobs:
         run: cd frontend && NODE_OPTIONS="--max-old-space-size=4096" npm run build
 
       - name: Upload build artifact
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v3
         with:
           name: frontend-dist
           path: frontend/dist
@@ -132,7 +138,7 @@ jobs:
         run: cd frontend && npm ci
 
       - name: Download frontend build
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v3
         with:
           name: frontend-dist
           path: frontend/dist
@@ -145,7 +151,7 @@ jobs:
 
       - name: Upload Playwright report
         if: always()
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v3
         with:
           name: playwright-report
           path: |