feat: implement dynamic sidebar with server-side menu translation

- Add server-side translation for menu labels using user's preferred_language
- Replace hardcoded sidebar template with dynamic rendering from menu API
- Remove hardcoded section/page mappings in favor of menu discovery
- Fix locale file structure (move menu keys to top level to avoid double-nesting)
- Sidebar now fully driven by /admin/menu-config/render/admin API endpoint

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

app/modules/core/static/admin/js/init-alpine.js

@@ -22,33 +22,21 @@ function data() {
 
   // ─────────────────────────────────────────────────────────────────
   // Sidebar sections persistence
+  // Dynamic - section IDs come from menu discovery API
   // ─────────────────────────────────────────────────────────────────
   const SIDEBAR_STORAGE_KEY = 'admin_sidebar_sections';
 
-  // Default state: Platform Administration open, others closed
-  const defaultSections = {
-    superAdmin: true,  // Super admin section (only visible to super admins)
-    platformAdmin: true,
-    vendorOps: false,
-    marketplace: false,
-    billing: false,
-    contentMgmt: false,
-    devTools: false,
-    platformHealth: false,
-    monitoring: false,
-    settingsSection: false
-  };
-
   function getSidebarSectionsFromStorage() {
     try {
       const stored = window.localStorage.getItem(SIDEBAR_STORAGE_KEY);
       if (stored) {
-        return { ...defaultSections, ...JSON.parse(stored) };
+        return JSON.parse(stored);
       }
     } catch (e) {
       console.warn('Failed to parse sidebar sections from localStorage:', e);
     }
-    return { ...defaultSections };
+    // Default: first section open (will be set dynamically)
+    return {};
   }
 
   function saveSidebarSectionsToStorage(sections) {
@@ -92,43 +80,18 @@ function data() {
     return null;
   }
 
-  // Map pages to their parent sections
-  const pageSectionMap = {
-    // Super Admin section
-    'admin-users': 'superAdmin',
-    // Platform Administration
-    companies: 'platformAdmin',
-    vendors: 'platformAdmin',
-    messages: 'platformAdmin',
-    // Vendor Operations (Products, Customers, Inventory, Orders, Shipping)
-    'marketplace-products': 'vendorOps',
-    'vendor-products': 'vendorOps',
-    customers: 'vendorOps',
-    inventory: 'vendorOps',
-    orders: 'vendorOps',
-    // Future: shipping will map to 'vendorOps'
-    // Marketplace
-    'marketplace-letzshop': 'marketplace',
-    // Content Management
-    'platform-homepage': 'contentMgmt',
-    'content-pages': 'contentMgmt',
-    'vendor-theme': 'contentMgmt',
-    // Developer Tools
-    components: 'devTools',
-    icons: 'devTools',
-    // Platform Health
-    testing: 'platformHealth',
-    'code-quality': 'platformHealth',
-    // Platform Monitoring
-    imports: 'monitoring',
-    'background-tasks': 'monitoring',
-    logs: 'monitoring',
-    'notifications-settings': 'monitoring',
-    // Platform Settings
-    settings: 'settingsSection',
-    profile: 'settingsSection',
-    'api-keys': 'settingsSection'
-  };
+  // Helper to find section ID for a page from menu data
+  function findSectionForPage(menuData, pageId) {
+    if (!menuData?.sections) return null;
+    for (const section of menuData.sections) {
+      for (const item of section.items || []) {
+        if (item.id === pageId) {
+          return section.id;
+        }
+      }
+    }
+    return null;
+  }
 
   return {
     // ─────────────────────────────────────────────────────────────────
@@ -191,9 +154,10 @@ function data() {
       saveSidebarSectionsToStorage(this.openSections);
     },
 
-    // Auto-expand section containing current page
+    // Auto-expand section containing current page (uses menu API data)
     expandSectionForCurrentPage() {
-      const section = pageSectionMap[this.currentPage];
+      if (!this.menuData) return;
+      const section = findSectionForPage(this.menuData, this.currentPage);
       if (section && !this.openSections[section]) {
         this.openSections[section] = true;
         saveSidebarSectionsToStorage(this.openSections);
@@ -242,12 +206,21 @@ function data() {
         this.menuData = await apiClient.get('/admin/menu-config/render/admin');
         // Build a set of visible menu item IDs for quick lookup
         this.visibleMenuItems = new Set();
-        for (const section of (this.menuData?.sections || [])) {
+        const sections = this.menuData?.sections || [];
+        for (const section of sections) {
           for (const item of (section.items || [])) {
             this.visibleMenuItems.add(item.id);
           }
+          // Initialize openSections for new sections (default: first section open)
+          if (this.openSections[section.id] === undefined) {
+            // Default: first section open, rest closed
+            this.openSections[section.id] = (sections.indexOf(section) === 0);
+          }
         }
         console.debug('Menu config loaded:', this.visibleMenuItems.size, 'items');
+
+        // Auto-expand section containing current page
+        this.expandSectionForCurrentPage();
       } catch (e) {
         // Silently fail - menu will show all items as fallback
         console.debug('Menu config not loaded, using defaults:', e?.message || e);

app/modules/core/static/admin/js/my-menu-config.js

@@ -57,9 +57,6 @@ function adminMyMenuConfig() {
         },
 
         async init() {
-            // Load i18n translations
-            await I18n.loadModule('core');
-
             // Guard against multiple initialization
             if (window._adminMyMenuConfigInitialized) {
                 myMenuConfigLog.warn('Already initialized, skipping');
@@ -70,6 +67,8 @@ function adminMyMenuConfig() {
             myMenuConfigLog.info('=== MY MENU CONFIG PAGE INITIALIZING ===');
 
             try {
+                // Load core translations for confirmations
+                await I18n.loadModule('core');
                 await this.loadMenuConfig();
                 myMenuConfigLog.info('=== MY MENU CONFIG PAGE INITIALIZED ===');
             } catch (error) {