fix(web): keep bulk checkbox selection across post navigation (openspec change keep-bulk-checkboxes)

- Save/restore checked candidate ids in sessionStorage (vesti_bulk_candidates / vesti_bulk_selected)
- Restore checks after page reload when opening a post via ?selected=N
- Fix selector: checkboxes live outside <form> (form=bulk-form attribute), query input[name=ids] globally
- Openspec: new capability candidates-bulk-selection, change archived

web/templates/candidates.html

@@ -196,14 +196,39 @@
 {% block scripts %}
 <script>
 (function(){
-  var boxes = document.querySelectorAll('#bulk-form input[name="ids"]');
+  var boxes = document.querySelectorAll('input[name="ids"]');
   var badge = document.getElementById('sel-count');
+  var KEY = 'vesti_bulk_candidates';
+  function selSet(){
+    var s = new Set();
+    try { s = new Set(JSON.parse(sessionStorage.getItem(KEY) || '[]')); } catch(e) {}
+    return s;
+  }
+  function saveSet(s){
+    try { sessionStorage.setItem(KEY, JSON.stringify(Array.from(s))); } catch(e) {}
+  }
   function upd(){
     var n = 0;
     for (var i = 0; i < boxes.length; i++) if (boxes[i].checked) n++;
     badge.textContent = n;
   }
-  for (var i = 0; i < boxes.length; i++) boxes[i].addEventListener('change', upd);
+  // Восстановить сохранённые отметки (кроме текущего, сервер уже отметил его)
+  var s = selSet();
+  for (var i = 0; i < boxes.length; i++){
+    if (s.has(boxes[i].value)) boxes[i].checked = true;
+  }
+  for (var i = 0; i < boxes.length; i++){
+    boxes[i].addEventListener('change', function(){
+      var st = selSet();
+      if (this.checked) st.add(this.value); else st.delete(this.value);
+      saveSet(st);
+      upd();
+    });
+  }
+  var form = document.getElementById('bulk-form');
+  if (form) form.addEventListener('submit', function(){
+    try { sessionStorage.removeItem(KEY); } catch(e) {}
+  });
   upd();
 })();
 </script>