refactor: Modularize MCP server with command batching

- Split monolithic mcp/server.py (1874 lines) into haproxy_mcp/ package:
  - config.py: Configuration constants and environment variables
  - exceptions.py: Custom exception classes
  - validation.py: Input validation functions
  - haproxy_client.py: HAProxy Runtime API client with batch support
  - file_ops.py: Atomic file operations with locking
  - utils.py: CSV parsing utilities
  - tools/: MCP tools organized by function
    - domains.py: Domain management (3 tools)
    - servers.py: Server management (7 tools)
    - health.py: Health checks (3 tools)
    - monitoring.py: Monitoring (4 tools)
    - configuration.py: Config management (4 tools)

- Add haproxy_cmd_batch() for sending multiple commands in single TCP connection
- Optimize server operations: 1 connection instead of 2 per server
- Optimize startup restore: All servers in 1 connection (was 2×N)
- Update type hints to Python 3.9+ style (built-in generics)
- Remove unused imports and functions
- Update CLAUDE.md with new structure and performance notes

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

haproxy_mcp/server.py

@@ -0,0 +1,36 @@
+#!/usr/bin/env python3
+"""HAProxy MCP Server - Direct Runtime API Integration
+
+This module provides an MCP (Model Context Protocol) server for managing HAProxy
+configuration and runtime state. It supports dynamic domain/server management
+with HTTP backends (SSL termination at HAProxy frontend).
+
+Environment Variables:
+    MCP_HOST: Host to bind MCP server (default: 0.0.0.0)
+    MCP_PORT: Port for MCP server (default: 8000)
+    HAPROXY_HOST: HAProxy Runtime API host (default: localhost)
+    HAPROXY_PORT: HAProxy Runtime API port (default: 9999)
+    HAPROXY_STATE_FILE: Path to server state file
+    HAPROXY_MAP_FILE: Path to domains.map file
+    HAPROXY_MAP_FILE_CONTAINER: Container path for domains.map
+    HAPROXY_SERVERS_FILE: Path to servers.json file
+    HAPROXY_POOL_COUNT: Number of pool backends (default: 100)
+    HAPROXY_MAX_SLOTS: Max servers per pool (default: 10)
+"""
+
+from mcp.server.fastmcp import FastMCP
+
+from .config import MCP_HOST, MCP_PORT
+from .tools import register_all_tools
+from .tools.configuration import startup_restore
+
+# Initialize MCP Server
+mcp = FastMCP("haproxy", host=MCP_HOST, port=MCP_PORT)
+
+# Register all tools
+register_all_tools(mcp)
+
+
+if __name__ == "__main__":
+    startup_restore()
+    mcp.run(transport="streamable-http")