Initial commit: WatchStack v0.1.0

- FastAPI + SQLite backend with REST API
- Polymorphic Media model (book + series)
- Cover lookup via Open Library
- Vanilla HTML/CSS/JS frontend (MAL-inspired)
- Dark theme, status tabs, drawer detail, stats modal
- 8 seed demo entries

app/database.py

@@ -0,0 +1,45 @@
+"""Datenbank-Engine und Session-Verwaltung."""
+from __future__ import annotations
+
+from pathlib import Path
+
+from sqlalchemy import create_engine
+from sqlalchemy.orm import DeclarativeBase, sessionmaker
+
+# SQLite-Datei liegt im data/-Ordner (gitignored).
+BASE_DIR = Path(__file__).resolve().parent.parent
+DATA_DIR = BASE_DIR / "data"
+DATA_DIR.mkdir(exist_ok=True)
+DB_PATH = DATA_DIR / "watchstack.db"
+
+DATABASE_URL = f"sqlite:///{DB_PATH}"
+
+engine = create_engine(
+    DATABASE_URL,
+    echo=False,
+    future=True,
+    connect_args={"check_same_thread": False},
+)
+
+SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False, expire_on_commit=False)
+
+
+class Base(DeclarativeBase):
+    """Basisklasse für alle ORM-Modelle."""
+
+
+def get_db():
+    """FastAPI-Dependency: liefert eine Session, schließt sie danach."""
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
+
+
+def init_db() -> None:
+    """Erstellt alle Tabellen, falls noch nicht vorhanden."""
+    # noqa: F401 – Modelle müssen importiert sein, damit sie bei Base.metadata registriert sind.
+    from app import models  # type: ignore[F401]
+
+    Base.metadata.create_all(bind=engine)