Add YouTube Music playlist import support

- Add ytmusicapi dependency for fetching public YouTube Music playlists
- Create youtube_music service with playlist fetching and track search
- Add /api/youtube-music/import and /api/youtube-music/search endpoints
- Add importYouTubePlaylist and searchYouTubeMusic API client functions
- Update Playlists page with YouTube Music import button and URL input modal

backend/app/api/endpoints/youtube_music.py

@@ -0,0 +1,110 @@
+from fastapi import APIRouter, Depends, HTTPException
+from pydantic import BaseModel
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.core.config import settings
+from app.core.database import get_db
+from app.core.security import get_current_user
+from app.models.user import User
+from app.models.playlist import Playlist
+from app.models.track import Track
+from app.services.youtube_music import get_playlist_tracks, search_track
+from app.services.recommender import build_taste_profile
+from app.schemas.playlist import PlaylistDetailResponse
+
+router = APIRouter(prefix="/youtube-music", tags=["youtube-music"])
+
+
+class ImportYouTubeRequest(BaseModel):
+    url: str
+
+
+class SearchYouTubeRequest(BaseModel):
+    query: str
+
+
+class YouTubeTrackResult(BaseModel):
+    title: str
+    artist: str
+    album: str | None = None
+    youtube_id: str | None = None
+    image_url: str | None = None
+
+
+@router.post("/import", response_model=PlaylistDetailResponse)
+async def import_youtube_playlist(
+    data: ImportYouTubeRequest,
+    user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    # Free tier limit
+    if not user.is_pro:
+        result = await db.execute(
+            select(Playlist).where(Playlist.user_id == user.id)
+        )
+        existing = list(result.scalars().all())
+        if len(existing) >= settings.FREE_MAX_PLAYLISTS:
+            raise HTTPException(
+                status_code=403,
+                detail="Free tier limited to 1 playlist. Upgrade to Pro for unlimited.",
+            )
+
+    # Fetch tracks from YouTube Music
+    try:
+        playlist_name, playlist_image, raw_tracks = get_playlist_tracks(data.url)
+    except ValueError as e:
+        raise HTTPException(status_code=400, detail=str(e))
+    except Exception:
+        raise HTTPException(status_code=400, detail="Failed to fetch playlist from YouTube Music. Make sure the URL is valid and the playlist is public.")
+
+    if not raw_tracks:
+        raise HTTPException(status_code=400, detail="Playlist is empty or could not be read.")
+
+    # Create playlist
+    playlist = Playlist(
+        user_id=user.id,
+        name=playlist_name,
+        platform_source="youtube_music",
+        external_id=data.url,
+        track_count=len(raw_tracks),
+    )
+    db.add(playlist)
+    await db.flush()
+
+    # Create tracks (no audio features available from YouTube Music)
+    tracks = []
+    for rt in raw_tracks:
+        track = Track(
+            playlist_id=playlist.id,
+            title=rt["title"],
+            artist=rt["artist"],
+            album=rt.get("album"),
+            image_url=rt.get("image_url"),
+        )
+        db.add(track)
+        tracks.append(track)
+
+    await db.flush()
+
+    # Build taste profile (without audio features, will be limited)
+    playlist.taste_profile = build_taste_profile(tracks)
+    playlist.tracks = tracks
+
+    return playlist
+
+
+@router.post("/search", response_model=list[YouTubeTrackResult])
+async def search_youtube_music(
+    data: SearchYouTubeRequest,
+    user: User = Depends(get_current_user),
+):
+    if not data.query.strip():
+        raise HTTPException(status_code=400, detail="Query cannot be empty")
+
+    try:
+        results = search_track(data.query.strip())
+    except Exception:
+        raise HTTPException(status_code=500, detail="Failed to search YouTube Music")
+
+    return results