Fix LLM reasoning mismatches by validating title and strengthening prompt

Add title validation in mood router to detect when the LLM returns reasoning
for a different movie than the jellyfin_id it selected. Also add explicit
prompt instruction to double-check reasoning matches the selected movie.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/routers/mood.py

@@ -83,6 +83,15 @@ async def get_mood_recommendations(request: Request, body: MoodRequest):
             continue
 
         movie = candidate_map[jf_id]
+
+        # Validate that the LLM's title matches the actual movie to catch mix-ups
+        rec_title = rec.get("title", "").strip().lower()
+        if rec_title and rec_title != movie.title.strip().lower():
+            logger.warning(
+                f"LLM title mismatch: returned '{rec.get('title')}' for jellyfin_id "
+                f"'{jf_id}' which is actually '{movie.title}' — skipping"
+            )
+            continue
         recommendations.append(
             Recommendation(
                 jellyfin_id=movie.jellyfin_id,