Enhance email templates with clickable links, branding, and improved styling

- Add clickable gallery links in all email templates
- Include application logo in email header and footer (custom or PicPeak default)
- Redesign emails with professional styling matching gallery login page
  - Gray background with white content box
  - PicPeak green header with centered logo
  - Clean typography and proper spacing
  - Responsive design for mobile devices
  - Styled call-to-action buttons
  - Footer with branding and copyright
- Update email processor to fetch branding settings dynamically
- Use proper API URLs for logo images in emails

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

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

backend/src/services/expirationChecker.js

@@ -3,6 +3,7 @@ const { db } = require('../database/db');
 const { archiveEvent } = require('./archiveService');
 const { queueEmail } = require('./emailProcessor');
 const logger = require('../utils/logger');
+const { formatDate } = require('../utils/dateFormatter');
 
 function startExpirationChecker() {
   // Check every hour for expired events and warnings
@@ -55,12 +56,15 @@ async function checkExpirations() {
 async function queueExpirationWarning(event) {
   const daysRemaining = Math.ceil((new Date(event.expires_at) - new Date()) / (1000 * 60 * 60 * 24));
   
+  // Determine language based on email domain
+  const emailLang = event.host_email.endsWith('.de') ? 'de' : 'en';
+  
   // Queue email to host
   await queueEmail(event.id, event.host_email, 'expiration_warning', {
-    host_name: event.host_email.split('@')[0],
+    host_name: event.host_name || event.host_email.split('@')[0],
     event_name: event.event_name,
     days_remaining: daysRemaining.toString(),
-    expiration_date: new Date(event.expires_at).toLocaleDateString(),
+    expiration_date: await formatDate(event.expires_at, emailLang),
     gallery_link: event.share_link
   });