fix(sqlite): WAL + busy_timeout 120s standardized across all labs

8개 lab의 _conn() 함수에 표준 동시성 패턴 통일:
- timeout=120.0 (connection 획득)
- PRAGMA journal_mode=WAL (reader/writer 분리)
- PRAGMA busy_timeout=120000 (트랜잭션 충돌 시 120초 대기)

stock-lab/screener/router.py 의 검증된 패턴(d9b6122) 을 lotto, stock-lab(메인),
music-lab, blog-lab, realestate-lab, agent-office, personal, travel-proxy 로 확산.
기존 'database is locked' 오류 윈도우를 흡수.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

music-lab/app/db.py

@@ -9,8 +9,10 @@ DB_PATH = "/app/data/music.db"
 
 def _conn() -> sqlite3.Connection:
     os.makedirs(os.path.dirname(DB_PATH), exist_ok=True)
-    conn = sqlite3.connect(DB_PATH)
+    conn = sqlite3.connect(DB_PATH, timeout=120.0)
     conn.row_factory = sqlite3.Row
+    conn.execute("PRAGMA journal_mode=WAL")
+    conn.execute("PRAGMA busy_timeout=120000")
     return conn