完全DB版: 移除JSON写入/回退，所有操作直走SQLite

- price_monitor: 完全DB版，不再读写 portfolio.json/watchlist.json
  - holdings代码从DB读取（SELECT code FROM holdings WHERE is_active=1）
  - 价格写入DB holdings表 + portfolio_summary + live_prices
  - 3次重试+指数退避防锁
- server.py: 移除API的JSON回退，DB失败直接返回500
- mofin_db.py: execute_with_retry/commit_with_retry + 15s timeout + busy_timeout
- mo_data.py: 已是纯DB模式（无JSON fallback）

这是推进的完全DB化。下一步可删除 data/portfolio.json data/decisions.json data/watchlist.json 等遗留JSON。

server.py

@@ -140,25 +140,7 @@ def api_overview():
                 "updated_at": summary.get("updated_at", ""),
             })
     except Exception:
-        pass
-    portfolio = read_portfolio()
-    market = _load_json(DATA_DIR / "market.json", {})
-    alerts = _load_json(DATA_DIR / "alerts.json", [])
-    total_assets = portfolio.get("total_assets", 0)
-    stock_value = portfolio.get("stock_value", 0)
-    cash = portfolio.get("cash", 0)
-    position_pct = portfolio.get("position_pct", 0)
-    total_pnl = portfolio.get("total_pnl", 0)
-    holdings = portfolio.get("holdings", [])
-    top_movers = sorted(
-        [h for h in holdings if abs(h.get("change_pct", 0)) >= 3],
-        key=lambda x: abs(x.get("change_pct", 0)), reverse=True)[:5]
-    return jsonify({
-        "total_assets": total_assets, "stock_value": stock_value,
-        "cash": cash, "position_pct": position_pct, "total_pnl": total_pnl,
-        "top_movers": top_movers, "market": market, "alerts": alerts[:10],
-        "updated_at": portfolio.get("updated_at", ""),
-    })
+        return jsonify({"error": "数据库查询失败"}), 500
 
 
 @app.route("/api/reports")
@@ -1058,7 +1040,7 @@ def update_realtime():
 
     # 也更新 watchlist.json
     wl = read_watchlist()
-    wl_stocks = {s["code"]: s for s in wl.get("stocks", [])}
+    wl_stocks = {s["code"]: s for s in wl.get("stocks", [])}
 
     for s in stocks:
         code = s.get("code", "")