fix(brain): ride out transient Claude 529 overloads

A single Claude 529 Overloaded dropped the voice turn straight to the apology
fallback. The anthropic SDK retries >=500/429 but only twice by default, which
a busy window can outlast. Raise max_retries (WSAI_BRAIN_MAX_RETRIES, default 4)
so transient overloads recover silently, and give overloads their own spoken
fallback ("서버가 붐벼서...") distinct from generic failures. Kept modest so a
sustained outage still fails fast instead of leaving the bot silent.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

wsai/dashboard.py

@@ -304,6 +304,10 @@ class Dashboard:
         except Exception as exc:  # noqa: BLE001
             log.exception("brain failed")
             self.monitor.log("error", f"두뇌 응답 실패: {exc}")
+            blob = f"{getattr(exc, 'status_code', '')} {exc}".lower()
+            if "529" in blob or "overload" in blob:
+                # Transient server overload survived the SDK retries.
+                return "지금 서버가 잠깐 붐벼서 생각이 늦네. 잠시 뒤에 다시 말해줄래?"
             return "미안, 지금 잠깐 생각이 안 났어. 다시 말해줄래?"
         if not text:
             return "음, 뭐라고 해야 할지 모르겠어. 다시 말해줄래?"