fix(M-AI-08): correct Prisma field names in snapshot builder

- DailyLearningActivity.date -> activityDate
- ReviewLog.rating is String, not Int (use parseInt)

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

src/modules/ai-job/learning-analysis-snapshot-builder.ts

@@ -183,7 +183,7 @@ export class LearningAnalysisSnapshotBuilder {
   private async aggregateStudyMetrics(userId: string, start: Date, end: Date) {
     try {
       const activities = await this.prisma.dailyLearningActivity.findMany({
-        where: { userId, date: { gte: start, lte: end } },
+        where: { userId, activityDate: { gte: start, lte: end } },
         select: { durationSeconds: true, activeRecallCount: true, reviewCount: true, readingSeconds: true },
       });
       const totalDuration = activities.reduce((s, a) => s + (a.durationSeconds || 0), 0);
@@ -208,7 +208,7 @@ export class LearningAnalysisSnapshotBuilder {
           take: 200,
         }),
       ]);
-      const ratings = reviews.filter(r => typeof r.rating === 'number').map(r => r.rating as number);
+      const ratings = reviews.map(r => parseInt(r.rating, 10)).filter(n => !isNaN(n));
       const accuracy = ratings.length > 0 ? ratings.filter(r => r >= 3).length / ratings.length : 0;
       return {
         reviewDueCount: dueCount,