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/GlobalThemeProvider.tsx

@@ -0,0 +1,33 @@
+import React, { useEffect, useRef } from 'react';
+import { useQuery } from '@tanstack/react-query';
+import { useTheme } from '../contexts/ThemeContext';
+import { api } from '../config/api';
+
+interface GlobalThemeProviderProps {
+  children: React.ReactNode;
+}
+
+export const GlobalThemeProvider: React.FC<GlobalThemeProviderProps> = ({ children }) => {
+  const { setTheme } = useTheme();
+  const themeAppliedRef = useRef(false);
+
+  // Fetch public settings including theme config
+  const { data: settingsData } = useQuery({
+    queryKey: ['global-theme-settings'],
+    queryFn: async () => {
+      const response = await api.get('/api/public/settings');
+      return response.data;
+    },
+    staleTime: 5 * 60 * 1000, // Cache for 5 minutes
+  });
+
+  // Apply global theme when settings are loaded
+  useEffect(() => {
+    if (!themeAppliedRef.current && settingsData?.theme_config) {
+      themeAppliedRef.current = true;
+      setTheme(settingsData.theme_config);
+    }
+  }, [settingsData, setTheme]);
+
+  return <>{children}</>;
+};