feat: add configurable currency locale and fix vendor JS init

Currency Locale Configuration:
- Add platform-level storefront settings (locale, currency)
- Create PlatformSettingsService with resolution chain:
  vendor → AdminSetting → environment → hardcoded fallback
- Add storefront_locale nullable field to Vendor model
- Update shop routes to resolve and pass locale to templates
- Add window.SHOP_CONFIG for frontend JavaScript access
- Centralize formatPrice() in shop-layout.js using SHOP_CONFIG
- Remove local formatPrice functions from shop templates

Vendor JS Bug Fix:
- Fix vendorCode being null on all vendor pages
- Root cause: page components overriding init() without calling parent
- Add parent init call to 14 vendor JS files
- Add JS-013 architecture rule to prevent future regressions
- Validator now checks vendor JS files for parent init pattern

Files changed:
- New: app/services/platform_settings_service.py
- New: alembic/versions/s7a8b9c0d1e2_add_storefront_locale_to_vendors.py
- Modified: 14 vendor JS files, shop templates, validation scripts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/api/v1/shop/profile.py

@@ -15,6 +15,7 @@ from app.api.deps import get_current_customer_api
 from app.core.database import get_db
 from app.exceptions import ValidationException
 from app.services.auth_service import AuthService
+from app.services.customer_service import customer_service
 from models.database.customer import Customer
 from models.schema.customer import (
     CustomerPasswordChange,
@@ -81,16 +82,10 @@ def update_profile(
 
     # If email is being changed, check uniqueness within vendor
     if update_data.email and update_data.email != customer.email:
-        existing = (
-            db.query(Customer)
-            .filter(
-                Customer.vendor_id == customer.vendor_id,
-                Customer.email == update_data.email,
-                Customer.id != customer.id,
-            )
-            .first()
+        existing = customer_service.get_customer_by_email(
+            db, customer.vendor_id, update_data.email
         )
-        if existing:
+        if existing and existing.id != customer.id:
             raise ValidationException("Email already in use")
 
     # Update only provided fields