Fix SQLite lock errors on /api/stats under concurrent writes.

Retry stats cache commits, serialize refresh, and fall back to read-only compute so the stats API does not return 500 when the database is briefly locked.

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

stats_engine.py

@@ -7,11 +7,16 @@
 from __future__ import annotations
 
 import json
+import threading
 from datetime import datetime
 from typing import Any, Optional
 
 from zoneinfo import ZoneInfo
 
+from db_conn import commit_retry, execute_retry
+
+_stats_refresh_lock = threading.Lock()
+
 TZ = ZoneInfo("Asia/Shanghai")
 
 STATS_VIEWS = [
@@ -288,13 +293,14 @@ def build_all_stats(conn, live_capital: float = 0.0) -> dict:
 
 
 def save_stats_cache(conn, data: dict) -> None:
-    conn.execute(
+    execute_retry(
+        conn,
         """INSERT INTO stats_cache (key, data_json, updated_at)
            VALUES ('all', ?, ?)
            ON CONFLICT(key) DO UPDATE SET data_json=excluded.data_json, updated_at=excluded.updated_at""",
         (json.dumps(data, ensure_ascii=False), data["updated_at"]),
     )
-    conn.commit()
+    commit_retry(conn)
 
 
 def load_stats_cache(conn) -> Optional[dict]:
@@ -310,6 +316,7 @@ def load_stats_cache(conn) -> Optional[dict]:
 
 
 def refresh_stats_cache(conn, live_capital: float = 0.0) -> dict:
-    data = build_all_stats(conn, live_capital)
-    save_stats_cache(conn, data)
-    return data
+    with _stats_refresh_lock:
+        data = build_all_stats(conn, live_capital)
+        save_stats_cache(conn, data)
+        return data