feat: implement admin-users management with super admin restriction

- Add /admin/admin-users routes for managing admin users (super admin only)
- Remove vendor role from user creation form (vendors created via company hierarchy)
- Add admin-users.html and admin-user-detail.html templates
- Add admin-users.js and admin-user-detail.js for frontend logic
- Move database operations to admin_platform_service (list, get, create, delete, toggle status)
- Update sidebar to show Admin Users section only for super admins
- Add isSuperAdmin computed property to init-alpine.js
- Fix /api/v1 prefix issues in JS files (apiClient already adds prefix)
- Update architecture rule JS-012 to catch more variable patterns (url, endpoint, path)
- Replace inline SVGs with $icon() helper in select-platform.html

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

static/admin/js/init-alpine.js

@@ -27,9 +27,11 @@ function data() {
 
   // 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,
@@ -75,12 +77,28 @@ function data() {
     }
   }
 
+  // Helper to get admin profile from localStorage
+  function getAdminProfileFromStorage() {
+    try {
+      // Check admin_user first (set by login), then adminProfile (legacy)
+      const stored = window.localStorage.getItem('admin_user') ||
+                     window.localStorage.getItem('adminProfile');
+      if (stored) {
+        return JSON.parse(stored);
+      }
+    } catch (e) {
+      console.warn('Failed to parse admin profile from localStorage:', e);
+    }
+    return null;
+  }
+
   // Map pages to their parent sections
   const pageSectionMap = {
+    // Super Admin section
+    'admin-users': 'superAdmin',
     // Platform Administration
     companies: 'platformAdmin',
     vendors: 'platformAdmin',
-    users: 'platformAdmin',
     messages: 'platformAdmin',
     // Vendor Operations (Products, Customers, Inventory, Orders, Shipping)
     'marketplace-products': 'vendorOps',
@@ -185,7 +203,16 @@ function data() {
     // ─────────────────────────────────────────────────────────────────
     // Page identifier - will be set by individual pages
     // ─────────────────────────────────────────────────────────────────
-    currentPage: ''
+    currentPage: '',
+
+    // ─────────────────────────────────────────────────────────────────
+    // Admin profile and super admin flag
+    // ─────────────────────────────────────────────────────────────────
+    adminProfile: getAdminProfileFromStorage(),
+
+    get isSuperAdmin() {
+      return this.adminProfile?.is_super_admin === true;
+    }
   }
 }