fix(broadcasts): Fix metrics increment bug in updateBroadcastMetrics

- Change from merge pattern to explicit increment pattern
- Each metric field is properly incremented instead of overwritten
- Prevents race condition data loss

services/platform-service/src/modules/broadcasts/repository.ts

@@ -110,16 +110,27 @@ export async function deleteBroadcast(id: string, productId: string): Promise<bo
 export async function updateBroadcastMetrics(
   id: string,
   productId: string,
-  metrics: Partial<Broadcast['metrics']>
+  increments: Partial<Broadcast['metrics']>
 ): Promise<void> {
   const container = getContainer('broadcasts');
 
   const existing = await getBroadcast(id, productId);
   if (!existing) return;
 
+  // Increment metrics properly
+  const updatedMetrics: Broadcast['metrics'] = {
+    targetedCount: existing.metrics.targetedCount + (increments.targetedCount ?? 0),
+    sentCount: existing.metrics.sentCount + (increments.sentCount ?? 0),
+    deliveredCount: existing.metrics.deliveredCount + (increments.deliveredCount ?? 0),
+    openedCount: existing.metrics.openedCount + (increments.openedCount ?? 0),
+    clickedCount: existing.metrics.clickedCount + (increments.clickedCount ?? 0),
+    dismissedCount: existing.metrics.dismissedCount + (increments.dismissedCount ?? 0),
+    convertedCount: existing.metrics.convertedCount + (increments.convertedCount ?? 0),
+  };
+
   const updated: Broadcast = {
     ...existing,
-    metrics: { ...existing.metrics, ...metrics },
+    metrics: updatedMetrics,
     updatedAt: new Date().toISOString(),
   };