Use host IP for backend test database URL in CI

The Postgres service container is not reachable via localhost from
inside the act runner container. Use the Docker host IP instead.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -52,7 +52,7 @@ jobs:
         run: uv run --python 3.14 --extra dev pytest -q
         working-directory: backend
         env:
-          TEST_DATABASE_URL: postgresql+asyncpg://postgres:postgres@localhost:5433/nuzlocke_test
+          TEST_DATABASE_URL: postgresql+asyncpg://postgres:postgres@192.168.1.10:5433/nuzlocke_test
 
   frontend-tests:
     runs-on: ubuntu-latest