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>

app/api/v1/admin/auth.py

@@ -141,7 +141,7 @@ def get_accessible_platforms(
         - For platform admins: Only assigned platforms
     """
     if current_user.is_super_admin:
-        platforms = db.query(Platform).filter(Platform.is_active == True).all()
+        platforms = admin_platform_service.get_all_active_platforms(db)
     else:
         platforms = admin_platform_service.get_platforms_for_admin(db, current_user.id)
 
@@ -184,14 +184,11 @@ def select_platform(
             "Super admins don't need platform selection - they have global access"
         )
 
-    # Verify admin has access to this platform
-    if not current_user.can_access_platform(platform_id):
-        raise InsufficientPermissionsException(
-            f"You don't have access to this platform"
-        )
+    # Verify admin has access to this platform (raises exception if not)
+    admin_platform_service.validate_admin_platform_access(current_user, platform_id)
 
     # Load platform
-    platform = db.query(Platform).filter(Platform.id == platform_id).first()
+    platform = admin_platform_service.get_platform_by_id(db, platform_id)
     if not platform:
         raise InvalidCredentialsException("Platform not found")