feat: Initial backend setup for Music Analyser

- Created FastAPI backend structure.
- Implemented Spotify Recently Played ingestion logic.
- Set up SQLite database with SQLAlchemy models.
- Added AI Service using Google Gemini.
- Created helper scripts for auth and background worker.
- Added Dockerfile and GitHub Actions workflow.

backend/app/schemas.py

@@ -0,0 +1,32 @@
+from pydantic import BaseModel
+from typing import List, Optional
+from datetime import datetime
+
+class TrackBase(BaseModel):
+    id: str
+    name: str
+    artist: str
+    album: str
+    duration_ms: int
+    popularity: Optional[int] = None
+    lyrics_summary: Optional[str] = None
+    genre_tags: Optional[str] = None
+
+class Track(TrackBase):
+    created_at: datetime
+    updated_at: datetime
+
+    class Config:
+        from_attributes = True
+
+class PlayHistoryBase(BaseModel):
+    track_id: str
+    played_at: datetime
+    context_uri: Optional[str] = None
+
+class PlayHistory(PlayHistoryBase):
+    id: int
+    track: Track
+
+    class Config:
+        from_attributes = True