Initial implementation of UniFi MCP Light server

Implements Hybrid MCP Light pattern with:
- 4 specific tools: list_clients, list_devices, get_system_info, get_network_health
- Meta tools: tool_index, api_call (raw API pass-through)
- API documentation resource at unifi://api-reference
- Starlette wrapper with /health endpoint
- Write protection (UNIFI_ALLOW_WRITES env var)
- UniFi OS auto-detection (proxy vs direct paths)
- Docker multi-stage build
- Gitea CI workflow

Closes #1, #2, #3, #4, #5, #7

.env.example

@@ -0,0 +1,12 @@
+# UniFi Controller Configuration
+UNIFI_HOST=192.168.1.1
+UNIFI_USERNAME=admin
+UNIFI_PASSWORD=your_password_here
+UNIFI_PORT=443
+UNIFI_SITE=default
+UNIFI_VERIFY_SSL=false
+
+# Security Settings
+# Enable write operations (POST, PUT, DELETE, PATCH) via unifi_api_call
+# Default: false (read-only mode)
+UNIFI_ALLOW_WRITES=false