RegWatch frontend : React/Vite -> nginx + Docker/CI homelab

- URL d'API externalisée (VITE_API_URL bakée au build), plus de localhost en dur
- Dockerfile multi-stage pnpm build -> nginx (fallback SPA)
- docker-compose (Watchtower) + .gitea/workflows/build.yml

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.dockerignore

@@ -0,0 +1,7 @@
+.git
+.env
+node_modules
+dist
+.gitea/
+docker-compose.yml
+.DS_Store