fix: clarify angry_wakeup_timer intent with TODO comment (Phase E Step 20)

- Change misleading 'Unused, kept for structural completeness' to
  'TODO: implement angry-wakeup mechanic or remove field'
- Field is dead code: never read or written in any Python code

bot/server_manager.py

@@ -39,7 +39,7 @@ class ServerConfig:
     previous_mood_name: str = "neutral"
     is_sleeping: bool = False
     sleepy_responses_left: Optional[int] = None
-    angry_wakeup_timer: Optional[float] = None  # Unused, kept for structural completeness
+    angry_wakeup_timer: Optional[float] = None  # TODO: implement angry-wakeup mechanic or remove field
     forced_angry_until: Optional[str] = None  # ISO format datetime string, or None
     just_woken_up: bool = False