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>

tests/unit/tools/test_certificates.py

@@ -1078,9 +1078,10 @@ class TestLoadCertToHaproxyError:
         pem_file = certs_dir / "example.com.pem"
         pem_file.write_text("cert content")
 
-        # Mock haproxy_cmd to raise exception
+        # Mock haproxy_cmd to raise HaproxyError
+        from haproxy_mcp.exceptions import HaproxyError
         with patch("haproxy_mcp.tools.certificates.CERTS_DIR", str(certs_dir)):
-            with patch("haproxy_mcp.tools.certificates.haproxy_cmd", side_effect=Exception("Connection failed")):
+            with patch("haproxy_mcp.tools.certificates.haproxy_cmd", side_effect=HaproxyError("Connection failed")):
                 from haproxy_mcp.tools.certificates import load_cert_to_haproxy
 
                 success, msg = load_cert_to_haproxy("example.com")

tests/unit/tools/test_configuration.py

@@ -547,7 +547,7 @@ class TestStartupRestoreFailures:
 
         with patch("socket.socket", return_value=mock_sock):
             with patch("haproxy_mcp.tools.configuration.restore_servers_from_config", return_value=0):
-                with patch("haproxy_mcp.tools.certificates.restore_certificates", side_effect=Exception("Certificate error")):
+                with patch("haproxy_mcp.tools.certificates.restore_certificates", side_effect=IOError("Certificate error")):
                     with caplog.at_level(logging.WARNING, logger="haproxy_mcp"):
                         from haproxy_mcp.tools.configuration import startup_restore
 
@@ -598,7 +598,7 @@ class TestHaproxyReloadFailures:
 
         with patch("socket.socket", return_value=mock_sock):
             with patch("haproxy_mcp.haproxy_client.reload_haproxy", return_value=(True, "Reloaded")):
-                with patch("haproxy_mcp.tools.configuration.restore_servers_from_config", side_effect=Exception("Restore failed")):
+                with patch("haproxy_mcp.tools.configuration.restore_servers_from_config", side_effect=OSError("Restore failed")):
                     with patch("time.sleep", return_value=None):
                         from haproxy_mcp.tools.configuration import register_config_tools
                         mcp = MagicMock()

tests/unit/tools/test_servers.py

@@ -756,8 +756,8 @@ class TestHaproxyAddServersRollback:
 
         def mock_configure_server_slot(backend, server_prefix, slot, ip, http_port):
             if slot == 2:
-                # Simulate unexpected error (not HaproxyError)
-                raise RuntimeError("Unexpected system error")
+                # Simulate unexpected error (IOError is caught by the exception handler)
+                raise IOError("Unexpected system error")
             configured_slots.append(slot)
             return f"{server_prefix}_{slot}"
 
@@ -807,7 +807,7 @@ class TestHaproxyAddServersRollback:
 
         def mock_configure_server_slot(backend, server_prefix, slot, ip, http_port):
             if slot == 2:
-                raise RuntimeError("Unexpected error")
+                raise OSError("Unexpected error")
             return f"{server_prefix}_{slot}"
 
         def mock_remove_server_from_config(domain, slot):