feat: auto-update sitemap when events are added/updated/removed

- Use tag-based cache for sitemap event list (events-sitemap)
- Add POST /api/revalidate endpoint (secret-protected) to trigger revalidation
- Backend calls revalidation after event create/update/delete
- Add REVALIDATE_SECRET to .env.example (frontend + backend)

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

frontend/.env.example

@@ -21,6 +21,10 @@ NEXT_PUBLIC_EMAIL=hola@spanglish.com.py
 NEXT_PUBLIC_TELEGRAM=spanglish_py
 NEXT_PUBLIC_TIKTOK=spanglishsocialpy
 
+# Revalidation secret (shared between frontend and backend for on-demand cache revalidation)
+# Must match the REVALIDATE_SECRET in backend/.env
+REVALIDATE_SECRET=change-me-to-a-random-secret
+
 # Plausible Analytics (optional - leave empty to disable tracking)
 NEXT_PUBLIC_PLAUSIBLE_URL=https://analytics.azzamo.net
 NEXT_PUBLIC_PLAUSIBLE_DOMAIN=spanglishcommunity.com

frontend/src/app/api/revalidate/route.ts

@@ -0,0 +1,27 @@
+import { revalidateTag } from 'next/cache';
+import { NextRequest, NextResponse } from 'next/server';
+
+export async function POST(request: NextRequest) {
+  try {
+    const body = await request.json();
+    const { secret, tag } = body;
+
+    // Validate the revalidation secret
+    const revalidateSecret = process.env.REVALIDATE_SECRET;
+    if (!revalidateSecret || secret !== revalidateSecret) {
+      return NextResponse.json({ error: 'Invalid secret' }, { status: 401 });
+    }
+
+    // Validate tag
+    const allowedTags = ['events-sitemap'];
+    if (!tag || !allowedTags.includes(tag)) {
+      return NextResponse.json({ error: 'Invalid tag' }, { status: 400 });
+    }
+
+    revalidateTag(tag);
+
+    return NextResponse.json({ revalidated: true, tag, now: Date.now() });
+  } catch {
+    return NextResponse.json({ error: 'Failed to revalidate' }, { status: 500 });
+  }
+}

frontend/src/app/sitemap.ts

@@ -12,7 +12,7 @@ interface Event {
 async function getPublishedEvents(): Promise<Event[]> {
   try {
     const response = await fetch(`${apiUrl}/api/events?status=published`, {
-      next: { revalidate: 3600 }, // Cache for 1 hour
+      next: { tags: ['events-sitemap'] },
     });
     if (!response.ok) return [];
     const data = await response.json();