feat: backend foundation setup with SQLite and FastAPI

backend/database.py

@@ -0,0 +1,24 @@
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker, declarative_base
+import os
+
+# Create data directory if it doesn't exist
+os.makedirs("data", exist_ok=True)
+
+SQLALCHEMY_DATABASE_URL = "sqlite:///./data/inventory.db"
+
+# connect_args={"check_same_thread": False} is required for SQLite in FastAPI/Starlette
+engine = create_engine(
+    SQLALCHEMY_DATABASE_URL, connect_args={"check_same_thread": False}
+)
+
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+Base = declarative_base()
+
+def get_db():
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()