refactor(monitoring): simplify brand dashboard and harden citation rendering

- drop brand_time_buckets and sparkline/coverage UI; dashboard now returns a single day
- compute mention rate from total actual samples instead of averaging per-platform rates
- canonicalize ai_platform_id across services and aggregate platform-overview snapshots
- strip mojibake and non-answer noise from callback payloads and question detail answers
- keep Kimi citations panel-only; still store raw search_results for audit
- render linked [n] inline citations for qwen/yuanbao answers with scroll-to-source behavior
- restrict立即采集 to today's business date with a clear i18n hint
- refresh content-citations into an ant-design table with truncation and hover styling

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/internal/tenant/app/monitoring_projection.go

@@ -55,7 +55,7 @@ func (s *MonitoringCallbackService) rebuildBrandDailyProjection(ctx context.Cont
 
 	desiredSampleCount := enabledQuestionCount * int64(len(platforms))
 	coverageRate := divideAsPointer(brandAgg.ActualSampleCount, brandAgg.PlannedSampleCount)
-	mentionRate := averageMonitoringPlatformMentionRate(platformAggs)
+	mentionRate := divideAsPointer(brandAgg.MentionedCount, brandAgg.ActualSampleCount)
 	top1MentionRate := divideAsPointer(brandAgg.Top1MentionedCount, brandAgg.ActualSampleCount)
 	firstRecommendRate := divideAsPointer(brandAgg.FirstRecommendedCount, brandAgg.ActualSampleCount)
 	positiveMentionRate := divideAsPointer(brandAgg.PositiveMentionedCount, brandAgg.ActualSampleCount)
@@ -151,7 +151,7 @@ func loadMonitoringProjectionPlatforms(ctx context.Context, businessPool *pgxpoo
 	if len(enabledJSON) > 0 {
 		var configured []string
 		if jsonErr := json.Unmarshal(enabledJSON, &configured); jsonErr == nil && len(configured) > 0 {
-			enabled = configured
+			enabled = monitoringPlatformIDs(defaultMonitoringPlatforms)
 		}
 	}
 
@@ -372,29 +372,6 @@ func (s *MonitoringCallbackService) loadMonitoringPlatformDailyAggregates(ctx co
 	return items, nil
 }
 
-func averageMonitoringPlatformMentionRate(items []monitoringPlatformDailyAggregate) *float64 {
-	if len(items) == 0 {
-		return nil
-	}
-
-	total := 0.0
-	count := 0
-	for _, item := range items {
-		rate := divideAsPointer(item.MentionedCount, item.ActualSampleCount)
-		if rate == nil {
-			continue
-		}
-		total += *rate
-		count++
-	}
-	if count == 0 {
-		return nil
-	}
-
-	average := total / float64(count)
-	return &average
-}
-
 func (s *MonitoringCallbackService) replaceMonitoringPlatformDailyProjection(ctx context.Context, tx pgx.Tx, tenantID, brandID int64, businessDate time.Time, items []monitoringPlatformDailyAggregate) error {
 	dateText := monitoringBusinessDateText(businessDate)