refactor(js): migrate JavaScript files to module directories

Move 47 JS files from static/{admin,vendor,shared}/js/ to their
respective module directories app/modules/*/static/*/js/:

- Orders: orders.js, order-detail.js
- Catalog: products.js (renamed from vendor-products.js), product-*.js
- Inventory: inventory.js (admin & vendor)
- Customers: customers.js, users.js, user-*.js
- Billing: billing-history.js, subscriptions.js, subscription-tiers.js,
  billing.js, invoices.js, feature-store.js, upgrade-prompts.js
- Messaging: messages.js, notifications.js, email-templates.js
- Marketplace: marketplace*.js, letzshop*.js, onboarding.js
- Monitoring: monitoring.js, background-tasks.js, imports.js, logs.js
- Dev Tools: testing-*.js, code-quality-*.js

Update 39 templates to reference new module static paths using
url_for('{module}_static', path='...') pattern.

Files staying in static/ (platform core):
- admin: dashboard, login, platforms, vendors, companies, admin-users,
  settings, components, init-alpine, module-config
- vendor: dashboard, login, profile, settings, team, media, init-alpine
- shared: api-client, utils, money, icons, log-config, vendor-selector,
  media-picker

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

app/templates/admin/user-edit.html

@@ -269,5 +269,5 @@
 {% endblock %}
 
 {% block extra_scripts %}
-<script src="{{ url_for('static', path='admin/js/user-edit.js') }}"></script>
+<script src="{{ url_for('customers_static', path='admin/js/user-edit.js') }}"></script>
 {% endblock %}