fix: workspace — removed topbar buttons, unified modals, parent_id support

- Topbar: removed New File/New Folder buttons + 'Files' label
- Breadcrumb: Workspace / work1 instead of work1 / Files
- Modals: single shared create modal with focus auto, @keydown.enter
- parent_id param: recursive folder/file creation inside folders
- Sidebar buttons use same POST /api/local-workspace/items
- newPageInWorkspace/newFolderInWorkspace now both use unified API

app/templates/base.html

@@ -631,7 +631,7 @@
           .catch(err => { alert('Failed to create sub-page: ' + err.message); });
       },
       newPageInWorkspace() {
-        const name = prompt('Page name:');
+        const name = prompt('File name:');
         if (!name || !name.trim()) return;
         fetch('/api/local-workspace/items', {
           method: 'POST',