### 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`
### What problem does this PR solve?
Add mcp self-host mode documentation, a complement of #7141.
### Type of change
- [x] Documentation Update
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Co-authored-by: writinwaters <93570324+writinwaters@users.noreply.github.com>
