fix: full force_rebuild 시 universe_snapshot 전체 삭제

tickers=None (전체 빌드)일 때 registry에서 제거된 stale 티커 데이터도
정리되도록 DELETE FROM universe_snapshot 실행.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/services/universe_service.py

@@ -290,14 +290,19 @@ class UniverseService:
             )
 
             if force_rebuild:
-                # Delete in chunks to avoid huge IN clauses
-                for i in range(0, len(ticker_list), _CHUNK):
-                    chunk = ticker_list[i:i + _CHUNK]
-                    await db.execute(
-                        UniverseSnapshot.__table__.delete().where(
-                            UniverseSnapshot.ticker.in_(chunk)
+                if not tickers:
+                    # Full rebuild: wipe ALL snapshots (also removes stale tickers
+                    # that were de-registered from the registry)
+                    await db.execute(UniverseSnapshot.__table__.delete())
+                else:
+                    # Partial rebuild: delete only the requested tickers
+                    for i in range(0, len(ticker_list), _CHUNK):
+                        chunk = ticker_list[i:i + _CHUNK]
+                        await db.execute(
+                            UniverseSnapshot.__table__.delete().where(
+                                UniverseSnapshot.ticker.in_(chunk)
+                            )
                         )
-                    )
                 await db.commit()
 
             # Load registry metadata (sector/industry/exchange/CIK)