fix: usar toIsoSqlUTC y corregir import de datetime

Co-authored-by: aider (openrouter/openai/gpt-5) <aider@aider.chat>

apps/web/src/lib/server/datetime.ts

@@ -1,4 +1,4 @@
-import { toIsoSqlUTC as coreToIsoSqlUTC } from '../../../../src/utils/datetime';
+import { toIsoSqlUTC as coreToIsoSqlUTC } from '../../../../../src/utils/datetime';
 
 /**
  * Serializa una fecha en UTC al formato SQL ISO "YYYY-MM-DD HH:MM:SS[.SSS]".

apps/web/src/routes/ics/group/[token].ics/+server.ts

@@ -65,7 +65,7 @@ export const GET: RequestHandler = async ({ params, request }) => {
   const inm = request.headers.get('if-none-match');
   if (inm && inm === etag) {
     // Actualizar last_used_at aunque sea 304
-    db.prepare(`UPDATE calendar_tokens SET last_used_at = ? WHERE id = ?`).run(toIsoSql(), row.id);
+    db.prepare(`UPDATE calendar_tokens SET last_used_at = ? WHERE id = ?`).run(toIsoSqlUTC(), row.id);
     return new Response(null, { status: 304, headers: { ETag: etag, 'Cache-Control': 'public, max-age=300' } });
   }