feat: add WonderQ admin backend

Add FastAPI admin/public API service, database setup, Docker deployment files, docs, and tests.

app/database.py

@@ -0,0 +1,21 @@
+from collections.abc import Generator
+from sqlalchemy import create_engine
+from sqlalchemy.orm import DeclarativeBase, Session, sessionmaker
+from .config import get_settings
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+settings = get_settings()
+engine = create_engine(settings.sqlalchemy_url, pool_pre_ping=True)
+SessionLocal = sessionmaker(bind=engine, autocommit=False, autoflush=False, expire_on_commit=False)
+
+
+def get_db() -> Generator[Session, None, None]:
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()