Add Bandcamp/YouTube links on all recs, Fix My Playlist, configurable rec count

- Bandcamp: match artist+song, fall back to artist-only page
- YouTube fallback: if not on Bandcamp, link to YouTube music video search
- Fix My Playlist: AI analyzes playlist, finds outliers, suggests replacements
- User chooses recommendation count (5, 10, 15, 20)

backend/app/schemas/recommendation.py

@@ -10,6 +10,7 @@ class RecommendationRequest(BaseModel):
     mode: str = "discover"  # discover, sonic_twin, era_bridge, deep_cuts, rising
     adventurousness: int = 3  # 1-5
     exclude: str | None = None  # comma-separated genres to exclude
+    count: int = 5  # Number of recommendations (5, 10, 15, 20)
 
 
 class RecommendationItem(BaseModel):
@@ -21,6 +22,7 @@ class RecommendationItem(BaseModel):
     preview_url: str | None = None
     image_url: str | None = None
     bandcamp_url: str | None = None
+    youtube_url: str | None = None
     reason: str
     score: float | None = None
     saved: bool = False