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")