fix: Gitea Traefik routing and connection pool optimization

- Remove middleware reference from Gitea Traefik labels (caused routing issues)
- Optimize Gitea connection pool settings (MAX_IDLE_CONNS=30, authentication_timeout=180s)
- Add explicit service reference in Traefik labels
- Fix intermittent 504 timeouts by improving PostgreSQL connection handling

Fixes Gitea unreachability via git.michaelschiemer.de

docs/troubleshooting/gitea-actions-artifact-compatibility.md

@@ -0,0 +1,33 @@
+# Gitea Actions Artifact Compatibility Issue
+
+## Problem
+
+Gitea Actions verwendet eine GHES (GitHub Enterprise Server) kompatible API. Die `@actions/artifact` Actions v2.0.0+ (insbesondere `upload-artifact@v4` und `download-artifact@v4`) werden auf GHES nicht unterstützt.
+
+### Fehlermeldung
+
+```
+GHESNotSupportedError: @actions/artifact v2.0.0+, upload-artifact@v4+ and download-artifact@v4+ are not currently supported on GHES.
+```
+
+## Lösung
+
+Verwende **v3** Versionen der Artifact Actions:
+
+- `actions/upload-artifact@v3` (statt `@v4`)
+- `actions/download-artifact@v3` (statt `@v4`)
+
+## Betroffene Workflows
+
+- `.gitea/workflows/build-image.yml` - 12 Vorkommen
+- `.gitea/workflows/monitor-performance.yml` - 1 Vorkommen
+
+## Migration
+
+Alle `@v4` Versionen wurden auf `@v3` downgraded. Die v3 Versionen sind vollständig kompatibel mit Gitea Actions und bieten die gleiche Funktionalität.
+
+## Referenzen
+
+- [Gitea Actions Documentation](https://docs.gitea.com/usage/actions/overview)
+- [GitHub Actions Artifact v3 Documentation](https://github.com/actions/upload-artifact/tree/v3)
+