Fix mobile responsiveness and implement enhanced theme system

- Fixed mobile gallery login box sizing and layout
- Fixed header button layout for mobile screens
- Fixed duplicate logo issue on logout
- Fixed '0' rendering when upload button is hidden
- Fixed horizontal scrolling on small screens

- Implemented comprehensive theme system with gallery layouts
- Added 6 different gallery layouts: Grid, Masonry, Carousel, Timeline, Hero, Mosaic
- Created enhanced theme customizer with layout selection
- Added theme presets for different event types
- Updated event creation with theme preview and customization
- Fixed all TypeScript compilation errors

- Added missing translation keys for create event page
- Added translations for theme customization features

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

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

frontend/src/i18n/locales/en.json

@@ -29,7 +29,9 @@
     "preview": "Preview",
     "processing": "Processing...",
     "upload": "Upload",
-    "days": "days"
+    "days": "days",
+    "customize": "Customize",
+    "hide": "Hide"
   },
   "upload": {
     "photoCategory": "Photo Category",
@@ -575,6 +577,7 @@
     "requiredFields": "Please fill in all required fields",
     "enterTestEmail": "Please enter a test email address",
     "failedToCreateEvent": "Failed to create event",
+    "eventCreationFailed": "Failed to create event",
     "networkError": "Network error. Please check your connection and try again.",
     "sessionExpired": "Session expired. Please login again."
   },