fix: always show activate button for non-current versions and in page header

- Header: 'Сделать активной' appears when current version is not the sole active one
- Versions table: button shown for all non-current versions regardless of is_active status

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

frontend/src/pages/TestEdit/index.tsx

@@ -117,6 +117,14 @@ export default function TestEdit() {
           К списку тестов
         </Button>
         <Space>
+          {versions.length > 1 && (!test.is_active || versions.some(v => v.id !== test.id && v.is_active)) && (
+            <Button
+              loading={isActivating}
+              onClick={() => activateVersion(test.id)}
+            >
+              Сделать активной
+            </Button>
+          )}
           <Button
             icon={<EditOutlined />}
             onClick={() => setEditMode(true)}
@@ -227,10 +235,10 @@ export default function TestEdit() {
                           Открыть
                         </Button>
                       )}
-                      {!record.is_active && (
+                      {record.id !== test.id && (
                         <Button
                           size="small"
-                          type="primary"
+                          type={record.is_active ? 'default' : 'primary'}
                           loading={isActivating}
                           onClick={() => activateVersion(record.id)}
                         >