Email queue + async sending; legal settings and placeholders

- Add in-memory email queue with rate limiting (MAX_EMAILS_PER_HOUR)
- Bulk send to event attendees now queues and returns immediately
- Frontend shows 'Emails are being sent in the background'
- Legal pages, settings, and placeholders updates

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/lib/legal.ts

@@ -102,7 +102,7 @@ export function getLegalPageFromFilesystem(slug: string, locale: string = 'en'):
 
 // Get a specific legal page content - tries API first, falls back to filesystem
 export async function getLegalPageAsync(slug: string, locale: string = 'en'): Promise<LegalPage | null> {
-  const apiUrl = process.env.NEXT_PUBLIC_API_URL || '';
+  const apiUrl = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:3001';
   
   // Try to fetch from API with locale parameter
   try {