refactor: CB 게이지 pnl_pct 저장 레이어를 L7 → L6_DAILY로 변경

portfolio_pnl_pct는 일별 성과 지표이므로 실시간 종목 데이터(L7)보다
일별 P&L 레이어(L6_DAILY)가 더 적합함. (PR #197 코드리뷰 반영)

- main.py: L7_REALTIME + ISO timestamp → L6_DAILY + date(YYYY-MM-DD)
- app.py: contexts 쿼리 layer/timeframe 조건 동기화
- tests: _seed_cb_context L6_DAILY + today 날짜로 수정

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

src/dashboard/app.py

@@ -85,11 +85,13 @@ def create_dashboard_app(db_path: str) -> FastAPI:
                 """
                 SELECT key, value
                 FROM contexts
-                WHERE layer = 'L7_REALTIME'
+                WHERE layer = 'L6_DAILY'
+                  AND timeframe = ?
                   AND key LIKE 'portfolio_pnl_pct_%'
                 ORDER BY updated_at DESC
                 LIMIT 20
-                """
+                """,
+                (today,),
             ).fetchall()
             current_pnl_pct: float | None = None
             if pnl_pct_rows:

src/main.py

@@ -430,10 +430,10 @@ async def trading_cycle(
             {"volume_ratio": candidate.volume_ratio},
         )
 
-    # Store latest pnl_pct in L7 so the dashboard can display the CB gauge
+    # Store latest pnl_pct in L6 (daily P&L layer) so the dashboard can display the CB gauge
     context_store.set_context(
-        ContextLayer.L7_REALTIME,
-        timeframe,
+        ContextLayer.L6_DAILY,
+        datetime.now(UTC).date().isoformat(),
         f"portfolio_pnl_pct_{market.code}",
         {"pnl_pct": round(pnl_pct, 4)},
     )