Add full-feature inline fallback when script.js fails

If external JS fails to load on some static hosts, run an inline version supporting add/edit/delete/favorite/search/sort/import/export/theme so the UI is never dead.

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

script.js

@@ -1,6 +1,8 @@
 (() => {
   "use strict";
 
+  // If index.html inline fallback already booted, do nothing.
+  if (globalThis.__LINKS_APP_BOOTED__) return;
   // Mark boot so index.html fallback won't run
   globalThis.__LINKS_APP_BOOTED__ = true;