Make next event visible to AI crawlers (SSR, JSON-LD, meta, llms.txt)

- SSR next event on homepage; pass initialEvent from server to avoid client-only content
- Add schema.org Event JSON-LD on homepage when next event exists
- Dynamic homepage metadata (description, OG, Twitter) with next event date
- Add dynamic /llms.txt route for AI-friendly plain-text event info
- Revalidation: support next-event tag; backend revalidates sitemap + next-event on event CUD
- Allow /llms.txt in robots.txt

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

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

@@ -12,15 +12,19 @@ export async function POST(request: NextRequest) {
       return NextResponse.json({ error: 'Invalid secret' }, { status: 401 });
     }
 
-    // Validate tag
-    const allowedTags = ['events-sitemap'];
-    if (!tag || !allowedTags.includes(tag)) {
+    // Validate tag(s) - supports single tag or array of tags
+    const allowedTags = ['events-sitemap', 'next-event'];
+    const tags: string[] = Array.isArray(tag) ? tag : [tag];
+    const invalidTags = tags.filter((t: string) => !allowedTags.includes(t));
+    if (tags.length === 0 || invalidTags.length > 0) {
       return NextResponse.json({ error: 'Invalid tag' }, { status: 400 });
     }
 
-    revalidateTag(tag);
+    for (const t of tags) {
+      revalidateTag(t);
+    }
 
-    return NextResponse.json({ revalidated: true, tag, now: Date.now() });
+    return NextResponse.json({ revalidated: true, tags, now: Date.now() });
   } catch {
     return NextResponse.json({ error: 'Failed to revalidate' }, { status: 500 });
   }