IT Assets: add role-based auth system and portal user sync

Auth:
- Fix local login (was redirecting to portal; now authenticates AdminUser directly)
- Portal SSO still takes priority in production via nginx headers

Role system (admin | editor | readonly):
- New app/utils/decorators.py with editor_required and admin_required decorators
- All write routes protected with editor_required (create/edit/delete/import/mask)
- Settings user management protected with admin_required
- Sidebar hides write-only links for readonly users
- Dashboard quick actions and list page buttons hidden for readonly

Settings page:
- Role colour badges (admin=red, editor=blue, readonly=grey)
- Inline role changer per user (dropdown auto-submit)
- Reset password modal per user
- Delete user button with confirmation
- Add user form includes role selector with legend

Portal user sync:
- New /internal/sync-user endpoint receives user pre-creation from portal
- INTERNAL_SYNC_SECRET added to config
- portal/config.py: added internal_url for itassets app so _sync_user_to_app works

IT_asset_management/app/__init__.py

@@ -38,6 +38,7 @@ def create_app(config_name='default'):
     from app.routes.audit import bp as audit_bp
     from app.routes.settings import bp as settings_bp
     from app.routes.doc_templates import bp as doc_templates_bp
+    from app.routes.internal import bp as internal_bp
 
     app.register_blueprint(auth_bp)
     app.register_blueprint(dashboard_bp)
@@ -48,6 +49,7 @@ def create_app(config_name='default'):
     app.register_blueprint(audit_bp)
     app.register_blueprint(settings_bp)
     app.register_blueprint(doc_templates_bp)
+    app.register_blueprint(internal_bp)
 
     # Inject common template variables
     from datetime import datetime, date