fix(experimentAnalysis): use ISO week start (Monday) consistently in aggregateWeeklyMetrics

- Change getWeekStartSunday to getISOWeekMonday for timestamp calculation
- Ensures week alignment between data aggregation and ISO week range calculation
- Fixes incorrect treatment_after average calculation

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

services/experimentAnalysis.ts

@@ -148,9 +148,10 @@ function aggregateWeeklyMetrics(
     const key = `${year}-W${String(weekNum).padStart(2, '0')}`;
 
     if (!weeklyMap.has(key)) {
+      // Use ISO week start (Monday) instead of Sunday for consistency
       weeklyMap.set(key, {
         week: key,
-        timestamp: getWeekStartSunday(year, weekNum),
+        timestamp: getISOWeekMonday(year, weekNum),
         units: 0,
         revenue: 0,
         adRevenue: 0,