feat: add initial setup wizard, workload insights, and policy audit mode

Add setup wizard with status tracking via SystemSetting model, implement /setup/status and /setup/complete endpoints to create initial admin user and optional cluster configuration, add workload insights endpoint with traffic analysis and policy matching including audit mode detection, implement enforcement_mode property on Policy model with audit/enforced states, add Modal component for dialogs, create SetupWizard page with multi

backend/app/seed/demo.py

@@ -14,6 +14,7 @@ from app.models.domain import (
     Role,
     SecurityGroup,
     ServiceCatalogItem,
+    SystemSetting,
     Subnet,
     Tenant,
     User,
@@ -44,6 +45,10 @@ SERVICES = [
 
 
 def seed_demo_data(db: Session) -> None:
+    if not db.get(SystemSetting, "setup"):
+        db.add(SystemSetting(key="setup", value={"complete": False}))
+        db.commit()
+
     if db.scalar(select(User).where(User.email == "admin@nexafabric.local")):
         return