feat: add MCP_RATE_LIMIT env variable to control MCP request rate

Document MCP_RATE_LIMIT in README, docker-compose, .env.example, Helm values and configmap.

README.md

@@ -160,6 +160,7 @@ services:
       # - DEMO_MODE=false # Enable demo mode (resets data hourly)
       # - ADMIN_EMAIL=admin@trek.local # Initial admin e-mail — only used on first boot when no users exist
       # - ADMIN_PASSWORD=changeme      # Initial admin password — only used on first boot when no users exist
+      # - MCP_RATE_LIMIT=60 # Max MCP API requests per user per minute (default: 60)
     volumes:
       - ./data:/app/data
       - ./uploads:/app/uploads
@@ -301,6 +302,7 @@ trek.yourdomain.com {
 | `ADMIN_PASSWORD` | Password for the first admin account created on initial boot. Must be set together with `ADMIN_EMAIL`. | random |
 | **Other** | | |
 | `DEMO_MODE` | Enable demo mode (hourly data resets) | `false` |
+| `MCP_RATE_LIMIT` | Max MCP API requests per user per minute | `60` |
 
 ## Optional API Keys