refactor: Extract large functions, improve exception handling, remove duplicates

## Large function extraction
- servers.py: Extract 8 _impl functions from register_server_tools (449 lines)
- certificates.py: Extract 7 _impl functions from register_certificate_tools (386 lines)
- MCP tool wrappers now delegate to module-level implementation functions

## Exception handling improvements
- Replace 11 broad `except Exception` with specific types
- health.py: (OSError, subprocess.SubprocessError)
- configuration.py: (HaproxyError, IOError, OSError, ValueError)
- servers.py: (IOError, OSError, ValueError)
- certificates.py: FileNotFoundError, (subprocess.SubprocessError, OSError)

## Duplicate code extraction
- Add parse_servers_state() to utils.py (replaces 4 duplicate parsers)
- Add disable_server_slot() to utils.py (replaces duplicate patterns)
- Update health.py, servers.py, domains.py to use new helpers

## Other improvements
- Add TypedDict types in file_ops.py and health.py
- Set file permissions (0o600) for sensitive files
- Update tests to use specific exception types

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

haproxy_mcp/validation.py

@@ -52,6 +52,18 @@ def validate_port(port: str) -> bool:
     return 1 <= port_num <= 65535
 
 
+def validate_port_int(port: int) -> bool:
+    """Validate port number as integer is in valid range.
+
+    Args:
+        port: Port number as integer
+
+    Returns:
+        True if port is valid (1-65535), False otherwise
+    """
+    return isinstance(port, int) and 1 <= port <= 65535
+
+
 def validate_backend_name(name: str) -> bool:
     """Validate backend or server name to prevent command injection.