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/utils.py

@@ -0,0 +1,29 @@
+"""Utility functions for HAProxy MCP Server."""
+
+from typing import Dict, Generator
+from .config import StatField
+
+
+def parse_stat_csv(stat_output: str) -> Generator[Dict[str, str], None, None]:
+    """Parse HAProxy stat CSV output into structured data.
+
+    Args:
+        stat_output: Raw output from 'show stat' command
+
+    Yields:
+        Dictionaries with parsed stat fields for each row
+    """
+    for line in stat_output.split("\n"):
+        if not line or line.startswith("#"):
+            continue
+        parts = line.split(",")
+        if len(parts) > StatField.STATUS:
+            yield {
+                "pxname": parts[StatField.PXNAME],
+                "svname": parts[StatField.SVNAME],
+                "scur": parts[StatField.SCUR] if len(parts) > StatField.SCUR else "0",
+                "smax": parts[StatField.SMAX] if len(parts) > StatField.SMAX else "0",
+                "status": parts[StatField.STATUS],
+                "weight": parts[StatField.WEIGHT] if len(parts) > StatField.WEIGHT else "0",
+                "check_status": parts[StatField.CHECK_STATUS] if len(parts) > StatField.CHECK_STATUS else "",
+            }