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/customers/routes/api/storefront.py

@@ -25,7 +25,7 @@ from app.core.database import get_db
 from app.core.environment import should_use_secure_cookies
 from app.exceptions import ValidationException
 from app.modules.core.services.auth_service import (
-    AuthService,  # MOD-004 - Core auth service
+    AuthService,  # noqa: MOD-004 - Core auth service
 )
 from app.modules.customers.models import PasswordResetToken
 from app.modules.customers.schemas import (
@@ -44,7 +44,7 @@ from app.modules.customers.services import (
     customer_service,
 )
 from app.modules.messaging.services.email_service import (
-    EmailService,  # MOD-004 - Core email service
+    EmailService,  # noqa: MOD-004 - Core email service
 )
 from app.modules.tenancy.exceptions import StoreNotFoundException
 from models.schema.auth import (