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/domains.py

@@ -13,14 +13,12 @@ from ..config import (
     WILDCARDS_MAP_FILE_CONTAINER,
     POOL_COUNT,
     MAX_SLOTS,
-    StateField,
-    STATE_MIN_COLUMNS,
     SUBPROCESS_TIMEOUT,
     CERTS_DIR,
     logger,
 )
 from ..exceptions import HaproxyError
-from ..validation import validate_domain, validate_ip
+from ..validation import validate_domain, validate_ip, validate_port_int
 from ..haproxy_client import haproxy_cmd
 from ..file_ops import (
     get_map_contents,
@@ -31,6 +29,7 @@ from ..file_ops import (
     remove_server_from_config,
     remove_domain_from_config,
 )
+from ..utils import parse_servers_state, disable_server_slot
 
 
 def _find_available_pool(entries: list[tuple[str, str]], used_pools: set[str]) -> Optional[str]:
@@ -166,18 +165,18 @@ def register_domain_tools(mcp):
         try:
             domains = []
             state = haproxy_cmd("show servers state")
+            parsed_state = parse_servers_state(state)
 
             # Build server map from HAProxy state
-            server_map: dict[str, list] = {}
-            for line in state.split("\n"):
-                parts = line.split()
-                if len(parts) >= STATE_MIN_COLUMNS and parts[StateField.SRV_ADDR] != "0.0.0.0":
-                    backend = parts[StateField.BE_NAME]
-                    if backend not in server_map:
-                        server_map[backend] = []
-                    server_map[backend].append(
-                        f"{parts[StateField.SRV_NAME]}={parts[StateField.SRV_ADDR]}:{parts[StateField.SRV_PORT]}"
-                    )
+            server_map: dict[str, list[str]] = {}
+            for backend, servers_dict in parsed_state.items():
+                for server_name, srv_info in servers_dict.items():
+                    if srv_info["addr"] != "0.0.0.0":
+                        if backend not in server_map:
+                            server_map[backend] = []
+                        server_map[backend].append(
+                            f"{server_name}={srv_info['addr']}:{srv_info['port']}"
+                        )
 
             # Read from domains.map
             seen_domains: set[str] = set()
@@ -220,7 +219,7 @@ def register_domain_tools(mcp):
             return "Error: Invalid domain format"
         if not validate_ip(ip, allow_empty=True):
             return "Error: Invalid IP address format"
-        if not (1 <= http_port <= 65535):
+        if not validate_port_int(http_port):
             return "Error: Port must be between 1 and 65535"
 
         # Use file locking for the entire pool allocation operation
@@ -339,8 +338,7 @@ def register_domain_tools(mcp):
             for slot in range(1, MAX_SLOTS + 1):
                 server = f"{backend}_{slot}"
                 try:
-                    haproxy_cmd(f"set server {backend}/{server} state maint")
-                    haproxy_cmd(f"set server {backend}/{server} addr 0.0.0.0 port 0")
+                    disable_server_slot(backend, server)
                 except HaproxyError as e:
                     logger.warning(
                         "Failed to clear server %s/%s for domain %s: %s",