Fix Forecast Period discrepancy by excluding month filter from seasonality data

App.tsx

@@ -233,7 +233,8 @@ const App: React.FC = () => {
       // Filter rawData to respect customer selections but keep all years (2025 for seasonality, 2026 for actuals)
       const forecastRelevantData = filterData(rawData, {
         ...filters,
-        year: [] // Ensure we don't filter out 2025/2026 if a single year is selected in UI
+        year: [], // Ensure we don't filter out 2025/2026 if a single year is selected in UI
+        month: [] // EXCLUDE month filtering to preserve seasonality calculation in calculateForecastViewData
       });
       handleForecastFetch(forecastRelevantData, rawData, filters);
     }