feat: multi-module improvements across merchant, store, i18n, and customer systems

- Fix platform-grouped merchant sidebar menu with core items at root level
- Add merchant store management (detail page, create store, team page)
- Fix store settings 500 error by removing dead stripe/API tab
- Move onboarding translations to module-owned locale files
- Fix onboarding banner i18n with server-side rendering + context inheritance
- Refactor login language selectors to use languageSelector() function (LANG-002)
- Move HTTPException handling to global exception handler in merchant routes (API-003)
- Add language selector to all login pages and portal headers
- Fix customer module: drop order stats from customer model, add to orders module
- Fix admin menu config visibility for super admin platform context
- Fix storefront auth and layout issues
- Add missing i18n translations for onboarding steps (en/fr/de/lb)

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

app/modules/loyalty/static/merchant/js/loyalty-settings.js

@@ -32,6 +32,9 @@ function merchantLoyaltySettings() {
             if (window._merchantLoyaltySettingsInitialized) return;
             window._merchantLoyaltySettingsInitialized = true;
 
+            // Load sidebar menu (from base data())
+            this.loadMenuConfig();
+
             await this.loadSettings();
             loyaltySettingsLog.info('=== MERCHANT LOYALTY SETTINGS PAGE INITIALIZATION COMPLETE ===');
         },