feat: implement MCP host configuration backup system

Add comprehensive backup and restore functionality for MCP host configuration files with atomic operations and Pydantic data validation.

Key components:
- MCPHostConfigBackupManager: Core backup management with timestamped backups
- AtomicFileOperations: Safe file operations with rollback capability
- BackupInfo/BackupResult: Pydantic models with validation
- BackupAwareOperation: Base class for backup-aware operations

Features:
- Automatic backup creation before configuration changes
- Manual backup restoration by hostname
- Backup listing and management with cleanup capabilities
- Atomic file operations preventing data corruption
- Support for all MCP host types (claude-desktop, claude-code, vscode, cursor, lmstudio, gemini)
- Microsecond-precision timestamps for unique backup identification

Backup location: ~/.hatch/mcp_host_config_backups/
Naming convention: mcp.json.<hostname>.<timestamp>

Resolves core backup system requirements from final design specification.

Author: LittleCoinCoin

hatch/mcp/__init__.py

@@ -0,0 +1,5 @@
+"""MCP (Model Context Protocol) support for Hatch.
+
+This module provides MCP host configuration management functionality,
+including backup and restore capabilities for MCP server configurations.
+"""