feat: add /health endpoint bypassing transport security

- Migrate from SSE to HTTP transport using fastmcp>=2.0
- Add /health endpoint for Docker health checks and load balancers
- Remove MCP_ALLOWED_HOSTS (no longer needed with http_app approach)
- Add lifespan handler for proper task group initialization
- Install curl in Docker image for health checks
- Update Makefile with test-health and test-mcp targets
- Update documentation to reflect new endpoint structure

Fixes: Health check fails with 421 Misdirected Request when
MCP_ALLOWED_HOSTS doesn't include localhost

README.md

@@ -52,24 +52,35 @@ All tools accept a `cluster` parameter. If only one cluster is configured, it's
 services:
   proxmox-mcp:
     image: gitea.ext.ben.io/b3nw/proxmox-mcp-custom:latest
-    environment:
-      - MCP_ALLOWED_HOSTS=proxmox-mcp.example.io,localhost:*
     volumes:
       - ./clusters.json:/app/clusters.json:ro
     ports:
       - "8000:8000"
+    healthcheck:
+      test: ["CMD", "curl", "-f", "http://localhost:8000/health"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
     restart: unless-stopped
 ```
 
 ### 3. Connect MCP Client
 
-SSE endpoint: `https://your-host/sse`
+MCP endpoint: `https://your-host/mcp`
+
+## Endpoints
+
+| Endpoint | Description |
+|----------|-------------|
+| `/mcp` | MCP HTTP endpoint |
+| `/health` | Health check endpoint for Docker/load balancers |
+
+The `/health` endpoint returns `{"status": "ok"}` (or `{"status": "degraded"}` if no clusters are configured) and is designed for Docker health checks.
 
 ## Environment Variables
 
 | Variable | Default | Description |
 |----------|---------|-------------|
-| `MCP_ALLOWED_HOSTS` | `localhost:*,127.0.0.1:*` | Allowed Host headers |
 | `CLUSTERS_CONFIG_PATH` | `/app/clusters.json` | Path to clusters config |
 
 ## Local Development
@@ -85,12 +96,12 @@ make dev
 
 # Test
 make logs
-make test-sse
+curl http://localhost:8001/health
 make stop
 ```
 
 ## Tech Stack
 
-- Python 3.11+ / FastMCP / proxmoxer
-- SSE transport / uvicorn
+- Python 3.11+ / FastMCP 2.0+ / proxmoxer
+- HTTP transport / uvicorn
 - Docker with multi-stage build