Exclude all previously recommended songs from new discoveries - no more repeats

backend/app/services/recommender.py

@@ -138,6 +138,14 @@ async def generate_recommendations(
             profile = build_taste_profile(all_tracks)
             taste_context = f"Taste profile from {len(all_tracks)} tracks:\n{json.dumps(profile, indent=2)}"
 
+    # Load ALL previously recommended songs to exclude duplicates
+    prev_recs_result = await db.execute(
+        select(Recommendation.artist, Recommendation.title).where(
+            Recommendation.user_id == user.id,
+        )
+    )
+    previously_recommended = {f"{r.artist} - {r.title}".lower() for r in prev_recs_result.all()}
+
     # Load disliked artists to exclude
     disliked_result = await db.execute(
         select(Recommendation.artist).where(
@@ -204,6 +212,9 @@ IMPORTANT: If the user mentions specific artists or songs in their request, do N
 
 Already in their library (do NOT recommend these):
 {', '.join(list(existing_tracks)[:50]) if existing_tracks else 'None provided'}
+
+ALREADY RECOMMENDED BEFORE (do NOT repeat any of these — every recommendation must be NEW):
+{', '.join(list(previously_recommended)[:100]) if previously_recommended else 'None yet'}
 {disliked_instruction}
 {exclude_instruction}