feat(auth): call ensure_default_admin on startup

backend/app/main.py

@@ -1,7 +1,10 @@
+from contextlib import asynccontextmanager
+
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 
-from app.database import Base, engine
+from app.auth import ensure_default_admin
+from app.database import Base, engine, SessionLocal
 from app.routes.auth import router as auth_router
 from app.routers.inventory import router as inventory_router
 from app.routers.relations import router as relations_router
@@ -10,10 +13,21 @@ from app.routers.jobs import router as jobs_router
 from app.routers.objects import router as objects_router
 from app.routers.health import router as health_router
 
-# Create all tables on startup
-Base.metadata.create_all(bind=engine)
 
-app = FastAPI(title="NetMapper API", version="0.1.0")
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    # Create all tables
+    Base.metadata.create_all(bind=engine)
+    # Seed default users if DB is empty
+    db = SessionLocal()
+    try:
+        ensure_default_admin(db)
+    finally:
+        db.close()
+    yield
+
+
+app = FastAPI(title="NetMapper API", version="0.1.0", lifespan=lifespan)
 
 app.add_middleware(
     CORSMiddleware,