Fix gallery issues: user uploads, error messages, and translations

- Fix user upload feature not showing in gallery
  - Add allow_user_uploads and upload_category_id to auth response
  - These fields are required for the gallery to show the upload button

- Improve gallery login error messages
  - Add specific translations for wrong password vs rate limiting
  - Map backend error messages to user-friendly translations
  - Added auth.wrongPassword and auth.tooManyAttempts keys

- Gallery pages already have full translation support
  - GalleryPage and GalleryView use i18n properly
  - All text is translated based on selected language

These fixes resolve:
1. User upload button not showing even when enabled
2. Generic error messages for wrong passwords
3. No feedback for rate limiting

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

Co-Authored-By: Claude <[email protected]>

frontend/src/pages/GalleryPage.tsx

@@ -66,7 +66,16 @@ export const GalleryPage: React.FC = () => {
         success: true
       });
     } catch (error: any) {
-      setLoginError(error.response?.data?.error || t('auth.invalidPassword'));
+      const errorMessage = error.response?.data?.error || 'Invalid password';
+      
+      // Map backend error messages to user-friendly translations
+      if (errorMessage.toLowerCase().includes('invalid password')) {
+        setLoginError(t('auth.wrongPassword'));
+      } else if (error.response?.status === 429 || errorMessage.toLowerCase().includes('too many')) {
+        setLoginError(t('auth.tooManyAttempts'));
+      } else {
+        setLoginError(t('auth.invalidPassword'));
+      }
       
       // Track failed password entry
       analyticsService.trackGalleryEvent('password_entry', {