Reduce gemini partial batch noise

backend/services/gemini_test.go

@@ -256,3 +256,12 @@ func TestExtractCompleteRecommendationObjectsReturnsNilWhenArrayMissing(t *testi
 		t.Fatalf("expected no objects, got %#v", got)
 	}
 }
+
+func TestGeminiVisionMaxOutputTokensShrinksForSingleCandidate(t *testing.T) {
+	if got := geminiVisionMaxOutputTokens(1); got != 180 {
+		t.Fatalf("expected 180 tokens for single candidate, got %d", got)
+	}
+	if got := geminiVisionMaxOutputTokens(4); got != 420 {
+		t.Fatalf("expected 420 tokens for four candidates, got %d", got)
+	}
+}