ci: restore simple workflow - rust runner now has Node.js

Updated in homelab: forgejo-runner-rust now uses docker:27-cli image
which includes Node.js + git + docker + full dev tools.

This allows actions/checkout@v4 and other GitHub Actions to work.

Workflow simplified:
- No container override (use runner's native environment)
- Uses actions/checkout@v4 (requires Node.js)
- Builds and pushes to registry

Test commit to verify new runner configuration works.

.gitea/workflows/build.yaml

@@ -9,9 +9,6 @@ jobs:
   build-and-push:
     name: Build and Push Image
     runs-on: rust
-    # NO container specified - use runner's native environment
-    # The rust runner has: Rust 1.83-bookworm + docker CLI + git
-    # Docker daemon available at: tcp://localhost:2376 (TLS)
     steps:
       - name: Checkout code
         uses: actions/checkout@v4