Fix/mcp doc (#7239)

### What problem does this PR solve?

This PR fixes an issue with the MCP server configuration in RAGFlow's
Docker deployment where:
1. Incorrect parameter naming (`--mcp--host-api-key` with double
hyphens) caused server startup failures
2. Port binding conflicts occurred due to unexposed MCP ports in Docker
3. Inconsistent host addressing between `0.0.0.0` and `127.0.0.1` led to
connectivity issues

The changes ensure proper MCP server initialization and reliable
inter-service communication.

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [ ] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):

### Key Changes

1. **Parameter Correction**:
   - Fixed `--mcp--host-api-key` → `--mcp-host-api-key`

docker/docker-compose.yml

     #   - --mcp-base-url=http://127.0.0.1:9380
     #   - --mcp-script-path=/ragflow/mcp/server/server.py
     #   - --mcp-mode=self-host
-    #   - --mcp--host-api-key="ragflow-xxxxxxx"
+    #   - --mcp-host-api-key="ragflow-xxxxxxx"
     container_name: ragflow-server
     ports:
       - ${SVR_HTTP_PORT}:9380

docs/develop/mcp.md

       - --mcp-base-url=http://127.0.0.1:9380
       - --mcp-script-path=/ragflow/mcp/server/server.py
       - --mcp-mode=self-host # `self-host` or `host`
-      - --mcp--host-api-key="ragflow-xxxxxxx" # only need to privide when mode is `self-host`
+      - --mcp-host-api-key="ragflow-xxxxxxx" # only need to privide when mode is `self-host`
 ```
 
 Then launch it normally `docker compose -f docker-compose.yml`.