fix: mark empty world cup calendar dates

platform/backend/app/main.py

@@ -3991,6 +3991,29 @@ async def _build_daily_card_calendar_payload(start_date: str = '2026-06-11', end
   dates: list[dict[str, Any]] = []
   for target_date in calendar_days:
     target_day = _to_date(target_date)
+    if match_counts[target_date] <= 0:
+      dates.append(
+        {
+          'date': target_date,
+          'match_count': 0,
+          'matched_matches': 0,
+          'recommendation_count': 0,
+          'live_count': 0,
+          'watch_count': 0,
+          'safe_single_count': 0,
+          'high_risk_single_count': 0,
+          'safe_parlay_count': 0,
+          'sgp_lottery_count': 0,
+          'total_amount_twd': 0,
+          'market_data_status': 'no_matches',
+          'snapshot_status': 'not_applicable',
+          'snapshot_item_count': 0,
+          'snapshot_preserved_count': 0,
+          'summary': '台北時間當日沒有世界盃賽事；保留此日期是為了讓賽程從開踢日起完整呈現。',
+        }
+      )
+      continue
+
     snapshot_payload = await _read_daily_recommendation_snapshot_payload(target_date)
     if target_day <= _taipei_today_date() and snapshot_payload and _all_daily_card_items(snapshot_payload):
       card = snapshot_payload