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>

app.py

@@ -45,7 +45,7 @@ from fee_specs import (
     purge_non_ctp_fee_rates,
 )
 from nav_settings import NAV_TOGGLES, get_nav_items, nav_enabled, save_nav_items
-from stats_engine import STATS_VIEWS, load_stats_cache, refresh_stats_cache
+from stats_engine import STATS_VIEWS, build_all_stats, load_stats_cache, refresh_stats_cache
 from kline_store import ensure_kline_tables
 from kline_stream import kline_hub, sse_format
 from kline_chart import generate_review_kline_chart, fetch_market_klines, MARKET_PERIODS
@@ -230,12 +230,20 @@ def touch_stats_cache():
 
 def get_stats_data() -> dict:
     conn = get_db()
-    capital = float(get_setting("live_capital", "0") or 0)
-    data = load_stats_cache(conn)
-    if not data:
-        data = refresh_stats_cache(conn, capital)
-    conn.close()
-    return data
+    try:
+        capital = float(get_setting("live_capital", "0") or 0)
+        data = load_stats_cache(conn)
+        if data:
+            return data
+        try:
+            return refresh_stats_cache(conn, capital)
+        except sqlite3.OperationalError as exc:
+            if "locked" not in str(exc).lower():
+                raise
+            app.logger.warning("stats cache refresh locked, compute without save: %s", exc)
+            return build_all_stats(conn, capital)
+    finally:
+        conn.close()
 
 
 def init_db():