Tune Gemini prompts for stock media search

backend/services/gemini.go

@@ -48,8 +48,12 @@ func (g *GeminiService) ExpandQuery(query string) ([]string, error) {
 				"parts": []map[string]string{
 					{
 						"text": `Return JSON only in this shape: {"querywords":["..."]}.
-Generate at most 4 concise search variations for media discovery across Google Video, Envato, and Artgrid.
-Keep the original language when possible. User query: ` + query,
+Generate at most 10 concise search variations for media discovery across Google Video, Envato, and Artgrid.
+If the user query is in Korean, include strong English search variants that a stock footage editor would use.
+Prioritize media, video footage, stock footage, cinematic b-roll, editorial footage, and scene-based search terms.
+Avoid celebrity gossip, reaction-style phrasing, clickbait phrasing, and generic web search wording.
+Mix Korean and English when useful, but make sure several queries are clean English production keywords.
+User query: ` + query,
 					},
 				},
 			},
@@ -57,7 +61,7 @@ Keep the original language when possible. User query: ` + query,
 		"generationConfig": map[string]any{
 			"responseMimeType": "application/json",
 			"temperature":      0.2,
-			"maxOutputTokens":  120,
+			"maxOutputTokens":  220,
 		},
 	}
 
@@ -125,7 +129,11 @@ func (g *GeminiService) Recommend(query string, candidates []SearchResult) ([]AI
 		{
 			"text": `Analyze the provided images for the user's search intent. Return JSON only in this shape:
 {"recommendations":[{"index":0,"reason":"short reason","recommended":true}]}
-Mark only the best matches as recommended=true. Keep reasons concise. Recommend up to 8 items. User query: ` + query,
+Mark only the best matches as recommended=true. Keep reasons concise. Recommend up to 8 items.
+Prefer cinematic b-roll, stock footage, editorial footage, clean composition, usable establishing shots, and professional media thumbnails.
+Avoid clickbait faces, exaggerated expressions, meme aesthetics, low-information thumbnails, sensational text overlays, or gossip-style imagery.
+Favor thumbnails that look directly useful for media editing and footage sourcing.
+User query: ` + query,
 		},
 	}