Fix cascading InFailedSQLTransactionError in covers forecast

When forecast_rooms_for_date throws inside covers_model, asyncpg aborts the
whole transaction. The exception was being caught with a warning but no rollback,
so every subsequent query in the same request failed. Added db.rollback() in
all three exception handlers (breakfast pickupv2, dinner pickupv2, per-day loop)
and moved public.py's rollback into a finally block so it always fires even
when covers_model returns normally with a corrupted transaction.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/api/public.py

@@ -384,8 +384,11 @@ async def get_revenue_forecast(
         covers_by_date = {c["date"]: c for c in covers_data.get("data", [])}
     except Exception as e:
         logger.warning(f"Covers forecast failed: {e}")
-        await db.rollback()
         covers_by_date = {}
+    finally:
+        # covers_model catches exceptions internally and may leave the transaction
+        # aborted without raising — always rollback so subsequent queries succeed
+        await db.rollback()
 
     # DOW averages from recent 8 weeks — fallback when covers gives zero for future dates
     dow_result = await db.execute(

backend/services/forecasting/covers_model.py

@@ -619,6 +619,7 @@ async def forecast_covers_for_date(
                 }
         except Exception as e:
             logger.warning(f"Pickupv2 forecast failed for {night_before}: {e}")
+            await db.rollback()
             # Fallback to prior year pattern
             breakfast_pickup = max(0, hotel_guests_prior - hotel_guests_otb)
             breakfast_forecast = breakfast_otb + breakfast_pickup
@@ -748,6 +749,7 @@ async def forecast_covers_for_date(
                 pickup_rooms = pickupv2_dinner.get('pickup_rooms_total', 0)
         except Exception as e:
             logger.warning(f"Pickupv2 forecast failed for dinner {target_date}: {e}")
+            await db.rollback()
 
         # Calculate forecasted hotel guests (OTB + pickup)
         pickup_guests = pickup_rooms * guests_per_room
@@ -840,6 +842,7 @@ async def forecast_covers_range(
             forecasts.append(day_forecast)
         except Exception as e:
             logger.warning(f"Failed to forecast covers for {current}: {e}")
+            await db.rollback()
 
         current += timedelta(days=1)