fix(i18n): translate remaining German hardcoded strings in PhotoUpload

Replace 6 hardcoded German strings in PhotoUpload.tsx with t() calls:
- 'Tag verknüpfen' → t('photos.linkDay')
- 'Kein Tag' / 'Tag N' → t('photos.noDay') / t('photos.dayLabel')
- '{N} Foto(s) ausgewählt' → t('photos.photoSelected/photosSelected')
- 'bis zu 30 Fotos' hint → t('photos.fileTypeHint')
- 'Wird hochgeladen...' → t('common.uploading')

Add all 6 new keys to all 14 language files and update test
assertions from German strings to English equivalents.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/src/components/Photos/PhotoUpload.test.tsx

@@ -50,7 +50,7 @@ describe('PhotoUpload', () => {
 
   it('FE-COMP-PHOTOUPLOAD-002: options section hidden before files are selected', () => {
     render(<PhotoUpload {...defaultProps} />)
-    expect(screen.queryByText('Tag verknüpfen')).not.toBeInTheDocument()
+    expect(screen.queryByText('Link Day')).not.toBeInTheDocument()
     expect(screen.queryByPlaceholderText('Optional caption...')).not.toBeInTheDocument()
   })
 
@@ -65,27 +65,27 @@ describe('PhotoUpload', () => {
     render(<PhotoUpload {...defaultProps} />)
     await uploadFiles([makeFile()])
     expect(screen.getByAltText('photo.jpg')).toBeInTheDocument()
-    expect(screen.getByText('Tag verknüpfen')).toBeInTheDocument()
+    expect(screen.getByText('Link Day')).toBeInTheDocument()
     expect(screen.getByPlaceholderText('Optional caption...')).toBeInTheDocument()
   })
 
   it('FE-COMP-PHOTOUPLOAD-005: file count label updates correctly', async () => {
     render(<PhotoUpload {...defaultProps} />)
     await uploadFiles([makeFile('photo1.jpg'), makeFile('photo2.jpg')])
-    expect(screen.getByText('2 Fotos ausgewählt')).toBeInTheDocument()
+    expect(screen.getByText('2 Photos selected')).toBeInTheDocument()
   })
 
   it('FE-COMP-PHOTOUPLOAD-006: remove button removes a file from preview', async () => {
     render(<PhotoUpload {...defaultProps} />)
     await uploadFiles([makeFile('photo1.jpg'), makeFile('photo2.jpg')])
-    expect(screen.getByText('2 Fotos ausgewählt')).toBeInTheDocument()
+    expect(screen.getByText('2 Photos selected')).toBeInTheDocument()
 
     // Remove buttons are inside `.relative.aspect-square` wrappers in the preview grid
     const removeButtons = document.querySelectorAll('.relative.aspect-square button')
     expect(removeButtons.length).toBe(2)
     await userEvent.click(removeButtons[0])
 
-    expect(screen.getByText('1 Foto ausgewählt')).toBeInTheDocument()
+    expect(screen.getByText('1 Photo selected')).toBeInTheDocument()
     expect(screen.getAllByRole('img').length).toBe(1)
   })
 
@@ -146,7 +146,7 @@ describe('PhotoUpload', () => {
     await userEvent.click(getSubmitButton())
 
     await waitFor(() => {
-      expect(screen.getByText(/wird hochgeladen/i)).toBeInTheDocument()
+      expect(screen.getAllByText(/uploading/i).length).toBeGreaterThan(0)
     })
 
     expect(getSubmitButton()).toBeDisabled()

client/src/components/Photos/PhotoUpload.tsx

@@ -90,7 +90,7 @@ export function PhotoUpload({ tripId, days, places, onUpload, onClose }: PhotoUp
           <>
             <p className="text-gray-600 font-medium">{t('photos.dropHereActive')}</p>
             <p className="text-gray-400 text-sm mt-1">{t('photos.clickToSelect')}</p>
-            <p className="text-gray-400 text-xs mt-2">JPG, PNG, WebP · max. 10 MB · bis zu 30 Fotos</p>
+            <p className="text-gray-400 text-xs mt-2">{t('photos.fileTypeHint')}</p>
           </>
         )}
       </div>
@@ -98,7 +98,7 @@ export function PhotoUpload({ tripId, days, places, onUpload, onClose }: PhotoUp
       {/* Preview grid */}
       {files.length > 0 && (
         <div>
-          <p className="text-sm font-medium text-gray-700 mb-2">{files.length} Foto{files.length !== 1 ? 's' : ''} ausgewählt</p>
+          <p className="text-sm font-medium text-gray-700 mb-2">{files.length} {t(files.length !== 1 ? 'photos.photosSelected' : 'photos.photoSelected')}</p>
           <div className="grid grid-cols-4 sm:grid-cols-6 gap-2 max-h-48 overflow-y-auto">
             {files.map((file, idx) => (
               <div key={idx} className="relative aspect-square group">
@@ -126,15 +126,15 @@ export function PhotoUpload({ tripId, days, places, onUpload, onClose }: PhotoUp
       {files.length > 0 && (
         <div className="grid grid-cols-2 gap-3">
           <div>
-            <label className="block text-xs font-medium text-gray-700 mb-1">Tag verknüpfen</label>
+            <label className="block text-xs font-medium text-gray-700 mb-1">{t('photos.linkDay')}</label>
             <select
               value={dayId}
               onChange={e => setDayId(e.target.value)}
               className="w-full border border-gray-200 rounded-lg px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-slate-900"
             >
-              <option value="">Kein Tag</option>
+              <option value="">{t('photos.noDay')}</option>
               {(days || []).map(day => (
-                <option key={day.id} value={day.id}>Tag {day.day_number}</option>
+                <option key={day.id} value={day.id}>{t('photos.dayLabel', { number: day.day_number })}</option>
               ))}
             </select>
           </div>
@@ -169,7 +169,7 @@ export function PhotoUpload({ tripId, days, places, onUpload, onClose }: PhotoUp
         <div className="bg-slate-50 rounded-lg p-3">
           <div className="flex items-center gap-2 mb-2">
             <div className="w-4 h-4 border-2 border-slate-900 border-t-transparent rounded-full animate-spin" />
-            <span className="text-sm text-slate-900">Wird hochgeladen...</span>
+            <span className="text-sm text-slate-900">{t('common.uploading')}</span>
           </div>
           <div className="w-full bg-slate-200 rounded-full h-1.5">
             <div