Expand backend debug logging

backend/services/ranker.go

@@ -119,6 +119,14 @@ func EvaluateAllCandidatesWithGemini(service *GeminiService, query string, ranke
 	if len(batches) == 0 {
 		return []AIRecommendation{}, stats, nil
 	}
+	if service != nil && service.Debug != nil {
+		service.Debug("ranker:gemini_batches_created", map[string]any{
+			"query":     query,
+			"limit":     limit,
+			"batches":   len(batches),
+			"chunkSize": chunkSize,
+		})
+	}
 
 	results := make([]batchResult, len(batches))
 	var wg sync.WaitGroup
@@ -143,6 +151,12 @@ func EvaluateAllCandidatesWithGemini(service *GeminiService, query string, ranke
 	seen := map[string]bool{}
 	for _, batch := range results {
 		if batch.err != nil {
+			if service != nil && service.Debug != nil {
+				service.Debug("ranker:gemini_batch_error", map[string]any{
+					"batchIndex": batch.index,
+					"error":      batch.err.Error(),
+				})
+			}
 			recovered, recoveredErrs := recoverGeminiBatchSequentially(service, query, ranked, batch.index*chunkSize)
 			if len(recovered) > 0 {
 				stats.SequentialRetried++
@@ -180,6 +194,9 @@ func EvaluateAllCandidatesWithGemini(service *GeminiService, query string, ranke
 		}
 	}
 	stats.RecommendedCount = len(merged)
+	if service != nil && service.Debug != nil {
+		service.Debug("ranker:gemini_batches_complete", stats)
+	}
 
 	switch {
 	case len(merged) > 0 && stats.Failed == 0: