fix: update docker-compose to use image reference

- docker-compose.yml now uses gitea.ext.ben.io/b3nw/gitea-mcp:latest
- Added docker-compose.dev.yml for local development builds

docker-compose.yml

@@ -1,12 +1,13 @@
 services:
   gitea-mcp:
-    build: .
+    image: gitea.ext.ben.io/b3nw/gitea-mcp:latest
     container_name: gitea-mcp
     restart: unless-stopped
     ports:
       - "8000:8000"
-    env_file:
-      - .env
+    environment:
+      - GITEA_URL=${GITEA_URL}
+      - GITEA_TOKEN=${GITEA_TOKEN}
     healthcheck:
       test: ["CMD", "curl", "-f", "http://localhost:8000/health"]
       interval: 30s