feat: submit all modal forms without page reload

- add a generic AJAX submitter for forms inside dialogs
- keep modal values and show field errors on server validation failure
- soft-refresh the page content on success, preserving scroll, search and filters
- share toast and re-init hooks for tables, markdown, sections and group page
- require passwords and add minlength/match validation on auth forms

web/src/main/resources/static/js/tablekit.js

@@ -192,8 +192,15 @@
         });
     }
 
-    document.addEventListener('DOMContentLoaded', function () {
+    function init() {
         document.querySelectorAll('table.tablekit').forEach(bind);
         document.querySelectorAll('input.table-search').forEach(bindSearch);
-    });
+    }
+    window.__lmsInitTablekit = init;
+
+    if (document.readyState === 'loading') {
+        document.addEventListener('DOMContentLoaded', init);
+    } else {
+        init();
+    }
 })();