docs: fix CLI reference documentation accuracy

- Fix MCP backup commands: host is now a required positional argument, not optional flag
- Fix hatch mcp backup restore: correct syntax from <backup-id> to <host> [--backup-file FILE]
- Fix hatch mcp backup clean: correct parameter name from --older-than to --older-than-days
- Remove non-existent --host parameter from hatch mcp list servers
- Document --env parameter in hatch mcp remove server as reserved for future use
- Clarify --include-tools and --exclude-tools use space-separated values, not comma-separated
- Add note that --older-than-days or --keep-count must be specified for backup clean

Author: LittleCoinCoin