Reapply "Strengthen search breadth and modal fitting"

This reverts commit 3f824c4bdf.

backend/services/ranker.go

@@ -97,7 +97,7 @@ func RankSearchResults(query string, results []SearchResult) []SearchResult {
 }
 
 func GeminiCandidateLimit(total int) int {
-	return min(total, 16)
+	return min(total, 24)
 }
 
 func EvaluateAllCandidatesWithGemini(service *GeminiService, query string, ranked []SearchResult) ([]AIRecommendation, GeminiBatchStats, error) {
@@ -291,7 +291,7 @@ func ReviewedRecommendationLinks(items []AIRecommendation) map[string]bool {
 }
 
 func RemainingGeminiCapacity(reviewed []AIRecommendation) int {
-	remaining := GeminiCandidateLimit(16) - len(ReviewedRecommendationLinks(reviewed))
+	remaining := GeminiCandidateLimit(24) - len(ReviewedRecommendationLinks(reviewed))
 	if remaining < 0 {
 		return 0
 	}