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/haproxy_client.py

@@ -67,8 +67,8 @@ def haproxy_cmd(command: str) -> str:
         raise HaproxyError("Invalid UTF-8 in response")
     except HaproxyError:
         raise
-    except Exception as e:
-        raise HaproxyError(str(e)) from e
+    except (OSError, BlockingIOError, BrokenPipeError) as e:
+        raise HaproxyError(f"Socket error: {e}") from e
 
 
 def haproxy_cmd_checked(command: str) -> str: