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/tools/configuration.py

@@ -117,7 +117,7 @@ def startup_restore() -> None:
         cert_count = restore_certificates()
         if cert_count > 0:
             logger.info("Restored %d certificates from config", cert_count)
-    except Exception as e:
+    except (HaproxyError, IOError, OSError, ValueError) as e:
         logger.warning("Failed to restore certificates: %s", e)
 
 
@@ -155,7 +155,7 @@ def register_config_tools(mcp):
         try:
             restored = restore_servers_from_config()
             return f"HAProxy configuration reloaded successfully ({restored} servers restored)"
-        except Exception as e:
+        except (HaproxyError, IOError, OSError, ValueError) as e:
             logger.error("Failed to restore servers after reload: %s", e)
             return f"HAProxy reloaded but server restore failed: {e}"