fix: repair broken loadConvs JS function in chat page

The function had an unclosed arrow function callback (convs.map(c => {)
followed by a misplaced catch, creating a JS syntax error that prevented
the entire <script> block from parsing — so no conversations or messages
rendered at all.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

admin/DashboardController.php

@@ -2122,13 +2122,7 @@ async function loadConvs() {
     const r = await fetch('/admin/chat?api=convs');
     if (!r.ok) return;
     const data = await r.json();
-    const convs = data.conversations || [];
-    if (convs.length === 0) {
-      list.innerHTML = '<div style="padding:24px 16px;text-align:center;color:#a0a8b8;font-size:13px">Sin conversaciones aún</div>';
-      return;
-    }
-    list.innerHTML = convs.map(c => {
-      renderConvs(convs);
+    renderConvs(data.conversations || []);
   } catch (e) {
     console.error('loadConvs error:', e);
   }