chore: update Docker configuration files with n8n API options

- Added n8n API configuration section to docker-compose.yml
- Updated .env.docker with n8n API environment variables
- Added helpful comments explaining the 16 additional management tools
- Configuration remains optional and commented out by default

This makes it easier for users to enable n8n management tools in Docker deployments.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

docker-compose.yml

@@ -23,6 +23,13 @@ services:
       # Database
       NODE_DB_PATH: ${NODE_DB_PATH:-/app/data/nodes.db}
       REBUILD_ON_START: ${REBUILD_ON_START:-false}
+      
+      # Optional: n8n API configuration (enables 16 additional management tools)
+      # Uncomment and configure to enable n8n workflow management
+      # N8N_API_URL: ${N8N_API_URL}
+      # N8N_API_KEY: ${N8N_API_KEY}
+      # N8N_API_TIMEOUT: ${N8N_API_TIMEOUT:-30000}
+      # N8N_API_MAX_RETRIES: ${N8N_API_MAX_RETRIES:-3}
     
     # Volumes for persistence
     volumes: