Complete translation implementation for admin interface

- Fixed all hardcoded strings in admin components to use t() function
- Updated BrandingPage.tsx to use translations for watermark settings
- Updated EventsListPage.tsx to use translations for status labels
- Added missing translation keys to both en.json and de.json
- Fixed translations for:
  - System settings (general, storage, categories tabs)
  - Branding page (watermark settings, positions, opacity)
  - Email configuration and templates
  - Event list view (status labels, filters, actions)
  - Event detail view (all sections properly translated)
- Added comprehensive German translations for all new keys
- Ensured consistent translation usage across all admin pages

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

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

frontend/src/components/admin/PhotoUpload.tsx

@@ -6,6 +6,7 @@ import { api } from '../../config/api';
 import { toast } from 'react-toastify';
 import { useQuery } from '@tanstack/react-query';
 import { categoriesService } from '../../services/categories.service';
+import { useTranslation } from 'react-i18next';
 
 interface PhotoUploadProps {
   eventId: number;
@@ -13,6 +14,7 @@ interface PhotoUploadProps {
 }
 
 export const PhotoUpload: React.FC<PhotoUploadProps> = ({ eventId, onUploadComplete }) => {
+  const { t } = useTranslation();
   const [isUploading, setIsUploading] = useState(false);
   const [selectedFiles, setSelectedFiles] = useState<File[]>([]);
   const [uploadProgress, setUploadProgress] = useState(0);
@@ -79,7 +81,7 @@ export const PhotoUpload: React.FC<PhotoUploadProps> = ({ eventId, onUploadCompl
       }
 
       // Show success message
-      toast.success(`Successfully uploaded ${selectedFiles.length} photo${selectedFiles.length > 1 ? 's' : ''}`);
+      toast.success(t('toast.uploadSuccess'));
       
       // Call callback
       if (onUploadComplete) {
@@ -87,7 +89,7 @@ export const PhotoUpload: React.FC<PhotoUploadProps> = ({ eventId, onUploadCompl
       }
     } catch (error: any) {
       console.error('Upload error:', error);
-      toast.error(error.response?.data?.error || 'Failed to upload photos');
+      toast.error(error.response?.data?.error || t('toast.uploadError'));
     } finally {
       setIsUploading(false);
       setUploadProgress(0);
@@ -105,17 +107,17 @@ export const PhotoUpload: React.FC<PhotoUploadProps> = ({ eventId, onUploadCompl
       {/* Category Selection */}
       <div>
         <label className="block text-sm font-medium text-neutral-700 mb-2">
-          Photo Category
+          {t('upload.photoCategory')}
         </label>
         <select
           value={selectedCategoryId || ''}
           onChange={(e) => setSelectedCategoryId(e.target.value ? Number(e.target.value) : null)}
           className="w-full px-3 py-2 border border-neutral-300 rounded-lg focus:ring-2 focus:ring-primary-500"
         >
-          <option value="">No category</option>
+          <option value="">{t('upload.noCategory')}</option>
           {categories.map((category) => (
             <option key={category.id} value={category.id}>
-              {category.name} {!category.is_global && '(Event specific)'}
+              {category.name} {!category.is_global && t('upload.eventSpecific')}
             </option>
           ))}
         </select>
@@ -132,10 +134,10 @@ export const PhotoUpload: React.FC<PhotoUploadProps> = ({ eventId, onUploadCompl
       >
         <Upload className="w-12 h-12 mx-auto text-neutral-400 mb-4" />
         <p className="text-neutral-700 font-medium mb-1">
-          Click to upload or drag and drop
+          {t('upload.clickToUpload')}
         </p>
         <p className="text-sm text-neutral-500">
-          JPEG, PNG or WebP (max 50MB per file)
+          {t('upload.fileRequirements')}
         </p>
         <input
           ref={fileInputRef}
@@ -151,7 +153,7 @@ export const PhotoUpload: React.FC<PhotoUploadProps> = ({ eventId, onUploadCompl
       {selectedFiles.length > 0 && (
         <div className="space-y-2">
           <p className="text-sm font-medium text-neutral-700">
-            Selected files ({selectedFiles.length})
+            {t('upload.selectedFiles')} ({selectedFiles.length})
           </p>
           <div className="max-h-48 overflow-y-auto space-y-2">
             {selectedFiles.map((file, index) => (
@@ -193,7 +195,7 @@ export const PhotoUpload: React.FC<PhotoUploadProps> = ({ eventId, onUploadCompl
           disabled={selectedFiles.length === 0 || isUploading}
           leftIcon={isUploading ? <Loader2 className="w-4 h-4 animate-spin" /> : <Upload className="w-4 h-4" />}
         >
-          {isUploading ? 'Uploading...' : `Upload ${selectedFiles.length} Photo${selectedFiles.length !== 1 ? 's' : ''}`}
+          {isUploading ? t('upload.uploading') : t('common.upload') + ` ${selectedFiles.length} ${t(selectedFiles.length === 1 ? 'common.photo' : 'common.photos')}`}
         </Button>
       </div>
 
@@ -201,7 +203,7 @@ export const PhotoUpload: React.FC<PhotoUploadProps> = ({ eventId, onUploadCompl
       {isUploading && (
         <div className="mt-4">
           <div className="flex justify-between text-sm text-neutral-600 mb-1">
-            <span>Uploading...</span>
+            <span>{t('upload.uploading')}</span>
             <span>{uploadProgress}%</span>
           </div>
           <div className="w-full bg-neutral-200 rounded-full h-2">