chore(lint): apply ruff --fix (4443 auto-fixes)

Auto-fixed categories:
- F401: unused imports removed
- I001: import blocks sorted
- W293: trailing whitespace stripped
- UP035: deprecated typing imports replaced
- SIM: simplify suggestions applied
- ARG: unused args prefixed with underscore
- T201: print statements removed
- F841: unused variables removed
- RUF059: unpacked variables prefixed

Remaining ~1500 unfixable errors (C901, B904, N806, E402) require manual work.

Backend smoke tests: 13/13 passed.

backend/src/core/ws_log_handler.py

@@ -3,9 +3,9 @@
 # @RELATION DEPENDS_ON -> [LogEntry]
 # @RELATION COMPOSES -> [CotJsonFormatter]
 import logging
-from typing import Dict, Any, List, Optional
 from collections import deque
 from datetime import datetime
+from typing import Any
 
 from pydantic import BaseModel, Field
 
@@ -15,7 +15,7 @@ class LogEntry(BaseModel):
     timestamp: datetime = Field(default_factory=datetime.utcnow)
     level: str
     message: str
-    context: Optional[Dict[str, Any]] = None
+    context: dict[str, Any] | None = None
 # #endregion LogEntry
 
 
@@ -58,7 +58,7 @@ class WebSocketLogHandler(logging.Handler):
 
     # #region WebSocketLogHandler.get_recent_logs [C:2] [TYPE Function] [SEMANTICS log,retrieve,buffer]
     # @BRIEF Returns a list of recent log entries from the buffer.
-    def get_recent_logs(self) -> List[LogEntry]:
+    def get_recent_logs(self) -> list[LogEntry]:
         """
         Returns a list of recent log entries from the buffer.
         """