fix: Transform sleep voice command duration to startTime/endTime format

Voice classification extracts duration in minutes, but sleep tracker expects
startTime/endTime. Added transformation logic to convert duration to proper
time range for sleep activities.

- Convert duration (minutes) to startTime + endTime timestamps
- Set default quality='good' and location='crib' if not specified
- Remove duration field after transformation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

maternal-web/components/voice/VoiceFloatingButton.tsx

@@ -173,11 +173,33 @@ export function VoiceFloatingButton() {
     const childId = children[0].id;
     console.log('[Voice] Using child ID:', childId);
 
+    // Transform sleep activity data - convert duration to startTime/endTime
+    let transformedDetails = { ...activityDetails };
+    const startTimestamp = activityTimestamp ? new Date(activityTimestamp) : new Date();
+
+    if (activityType === 'sleep' && activityDetails.duration) {
+      const durationMinutes = Number(activityDetails.duration);
+      const endTime = new Date(startTimestamp.getTime() + durationMinutes * 60 * 1000);
+
+      transformedDetails = {
+        ...activityDetails,
+        startTime: startTimestamp.toISOString(),
+        endTime: endTime.toISOString(),
+        quality: activityDetails.quality || 'good',
+        location: activityDetails.location || 'crib',
+      };
+
+      // Remove duration as it's now represented by startTime/endTime
+      delete transformedDetails.duration;
+
+      console.log('[Voice] Transformed sleep data - duration', durationMinutes, 'minutes to startTime/endTime');
+    }
+
     // Create the activity - use frontend API format (trackingApi transforms to backend DTO)
     const activityData = {
       type: activityType,
-      timestamp: activityTimestamp ? new Date(activityTimestamp).toISOString() : new Date().toISOString(),
-      data: activityDetails,
+      timestamp: startTimestamp.toISOString(),
+      data: transformedDetails,
       notes: activityDetails.notes || undefined,
     };