fix(lint): restore noqa directives and register custom codes with ruff

Reverts the noqa: removal — the architecture validators (SVC-006,
SEC-034, MOD-004, API-007) use these to skip known-safe violations.
Added ruff lint.external config so ruff treats them as valid codes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/modules/tenancy/routes/api/admin_users.py

@@ -22,7 +22,7 @@ from app.api.deps import get_current_super_admin, get_current_super_admin_api
 from app.core.database import get_db
 from app.exceptions import ValidationException
 from app.modules.tenancy.models import (
-    User,  # API-007 - Internal helper uses User model
+    User,  # noqa: API-007 - Internal helper uses User model
 )
 from app.modules.tenancy.services.admin_platform_service import admin_platform_service
 from models.schema.auth import UserContext