fix: workspace page redesign — modals, folder distinction, no duplication

- Complete redesign of local_workspace.html
- Modal dialogs (Create File, Create Folder, Rename, Delete) — no prompt()
- Folder creation fixed: parent_section='Workspace' → 📁 icon
- Tree API properly detects folders via parent_section
- No duplicate empty state — unified header + empty message
- Professional UI with backdrop blur, focus auto, disabled btn

app/routers/dashboard.py

@@ -528,9 +528,11 @@ async def local_workspace_tree(request: Request):
     for r in roots:
         with get_conn() as conn:
             children = conn.execute(
-                "SELECT id, title FROM pages WHERE parent_id=? ORDER BY created_at", (r["id"],)
+                "SELECT id, title, parent_section FROM pages WHERE parent_id=? ORDER BY created_at", (r["id"],)
             ).fetchall()
-        item = {"id": r["id"], "name": r["title"] or "Untitled", "type": "page",
+        is_folder = r.get("parent_section") == "Workspace"
+        rtype = "folder" if is_folder else "page"
+        item = {"id": r["id"], "name": r["title"] or "Untitled", "type": rtype,
                 "children": [{"id": c["id"], "name": c["title"] or "Untitled", "type": "page"} for c in children]}
         tree.append(item)
     return {"tree": tree}