修复模拟盘卖币握锁导致 database is locked 与中控超时离线。

Co-authored-by: Cursor <cursoragent@cursor.com>

app.py

@@ -1611,6 +1611,9 @@ def get_db():
     conn.row_factory = sqlite3.Row
     try:
         conn.execute("PRAGMA busy_timeout=30000")
+        # WAL:读(中控快照)与写(卖币/同步)可并行,避免 database is locked→全部超时离线
+        conn.execute("PRAGMA journal_mode=WAL")
+        conn.execute("PRAGMA synchronous=NORMAL")
     except Exception:
         pass
     return conn
@@ -5119,11 +5122,14 @@ def background_task():
     while True:
         try:
             auto_transfer_once_per_day()
-            conn = get_db()
+            # force_close 自带连接,勿套在另一未关闭连接上
             force_close_before_reset()
-            reconcile_external_closes(conn)
-            conn.commit()
-            conn.close()
+            conn = get_db()
+            try:
+                reconcile_external_closes(conn)
+                conn.commit()
+            finally:
+                conn.close()
             check_key_monitors()
             check_order_monitors()
         except Exception as e: