fix: extract render_workspace_tree macro, fix sidebar-tree endpoint

- Extracted render_workspace_tree macro into _workspace_tree_macro.html
  so it can be imported independently from base.html (which has many
  template variables like user, workspace_name, etc.)
- Fixed GET /api/sidebar/workspace-tree to use the extracted macro
- Added error logging for easier debugging

app/routers/dashboard.py

@@ -1554,15 +1554,16 @@ async def sidebar_workspace_tree(request: Request):
                 '<span class="page-name text-dim">No pages yet</span></li>'
             )
         
-        # Render the tree using the same Jinja2 macro as base.html
+        # Render the tree using the extracted macro
         env = Environment(loader=FileSystemLoader("app/templates"))
         template = env.from_string(
-            "{% from 'base.html' import render_workspace_tree %}"
+            "{% from '_workspace_tree_macro.html' import render_workspace_tree %}"
             "{{ render_workspace_tree(pages) }}"
         )
         html = template.render(pages=pages)
         return HTMLResponse(html)
-    except (ValueError, Exception):
+    except (ValueError, Exception) as e:
+        logger.error(f"sidebar_workspace_tree failed: {e}", exc_info=True)
         return HTMLResponse(
             '<li class="sidebar-item empty-hint"><span class="page-icon">📄</span>'
             '<span class="page-name text-dim">No pages yet</span></li>'