ci: check sqlx queries against live db

.github/workflows/backend.yml

@@ -27,12 +27,12 @@ jobs:
     env:
       DATABASE_URL: postgres://postgres:pass@localhost:5432/loft_test
       STORAGE_PATH: /tmp/loft-files-test
-      SQLX_OFFLINE: "true"
 
     steps:
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable
       - run: cargo install sqlx-cli --no-default-features --features postgres,rustls
+      - run: cargo sqlx prepare
       - run: sqlx migrate run
       - run: mkdir -p /tmp/loft-files-test
       - run: cargo test