Add stable /next and /featured URLs that redirect to the current event.

These short links always resolve to the latest upcoming or featured event so they can be shared without updating when events rotate.

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

backend/src/index.ts

@@ -673,11 +673,21 @@ const openApiSpec = {
         },
       },
     },
+    '/api/events/next': {
+      get: {
+        tags: ['Events'],
+        summary: 'Get next upcoming event (chronological)',
+        description: 'Get the single earliest upcoming published event, ignoring featured promotion.',
+        responses: {
+          200: { description: 'Next event or null' },
+        },
+      },
+    },
     '/api/events/next/upcoming': {
       get: {
         tags: ['Events'],
         summary: 'Get next upcoming event',
-        description: 'Get the single next upcoming published event.',
+        description: 'Get the featured event if valid, otherwise the single next upcoming published event.',
         responses: {
           200: { description: 'Next event or null' },
         },