feat: recursive tree, drag & drop, sub-folders in sidebar workspace

- _load_workspace_pages now recursively loads children via _load_children()
- Sidebar: recursive Jinja2 macro render_workspace_tree()
- Drag & drop: HTML5 DnD — drag files into folders or reorder
- move API: PUT /api/local-workspace/items/{id}/move
- Folder hover shows 📄 (new file) + 📁 (sub-folder) buttons
- newPageInFolder/newFolderInFolder with parent_id for nesting
- Visual: dragging opacity + drop target highlight
- Items indented by depth (16px per level)

app/routers/dashboard.py

@@ -581,6 +581,21 @@ async def delete_local_workspace_item(request: Request, item_id: int):
     return {"status": "ok"}
 
 
+@router.put("/api/local-workspace/items/{item_id:int}/move")
+async def move_local_workspace_item(request: Request, item_id: int):
+    """Move an item to a new parent (drag & drop)."""
+    import json
+    body = await request.json()
+    new_parent_id = body.get("parent_id")  # None = move to root
+    with get_conn() as conn:
+        conn.execute(
+            "UPDATE pages SET parent_id=? WHERE id=?",
+            (new_parent_id, item_id),
+        )
+        conn.commit()
+    return {"status": "ok"}
+
+
 # ═══════════ Workspaces CRUD ═══════════
 
 WORKSPACE_COOKIE = "flowdeck_workspace"