Fix brand theme application and add comprehensive translations

- Fixed theme not being reflected on gallery and admin login pages
- Created GlobalThemeProvider to apply themes globally
- Updated gallery and admin login pages to use dynamic CSS variables
- Added complete translations for all admin sections in English and German:
  - Notifications management
  - Event view and creation
  - Photo upload functionality
  - Category management
  - Archive page view
  - Analytics dashboard
  - Branding and theme settings
  - System settings
  - CMS page management
  - Email configuration
- Fixed admin photo management display issues
- Fixed photo upload category assignment
- Added password reset functionality for galleries
- Improved error handling and user feedback

🤖 Generated with [Claude Code](https://claude.ai/code)

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

frontend/src/components/admin/AdminLayout.tsx

@@ -2,12 +2,17 @@ import React, { useState } from 'react';
 import { Outlet, Navigate } from 'react-router-dom';
 
 import { useAdminAuth } from '../../contexts';
+import { useSessionTimeout } from '../../hooks/useSessionTimeout';
 import { AdminSidebar } from './AdminSidebar';
 import { AdminHeader } from './AdminHeader';
+import { MaintenanceBanner } from './MaintenanceBanner';
 
 export const AdminLayout: React.FC = () => {
   const { isAuthenticated, isLoading } = useAdminAuth();
   const [sidebarOpen, setSidebarOpen] = useState(false);
+  
+  // Handle session timeout
+  useSessionTimeout();
 
   if (isLoading) {
     return (
@@ -41,6 +46,9 @@ export const AdminLayout: React.FC = () => {
       <div className="flex-1 flex flex-col min-w-0">
         {/* Header */}
         <AdminHeader onMenuClick={() => setSidebarOpen(true)} />
+        
+        {/* Maintenance mode banner */}
+        <MaintenanceBanner />
 
         {/* Page content */}
         <main id="main-content" className="flex-1 px-4 sm:px-6 lg:px-8 py-8">