Feat v0.4.1 folders navigation tree (#23)

Add folders as a first-class concept in the Notes surface with full
CRUD, nested tree navigation, and folder-based note filtering.

Backend (script.star):
- Folder CRUD handlers: list, create, update, delete
- Move-note endpoint to reassign folder_id
- Delete cascades: orphan notes to unfiled, reparent child folders
- Stats now include unfiled and folder counts

Frontend (js/main.js):
- FolderTree component with flat-to-tree builder via useMemo
- FolderNode recursive component with expand/collapse, inline rename
- Folder state: activeFolderId, showUnfiled for sidebar filtering
- Editor folder select dropdown for moving notes between folders
- New notes inherit active folder on creation

Schema (manifest.json):
- New ext_notes_folders table (name, parent_id, creator_id, sort_order)
- 5 new API routes: GET/POST /folders, PUT/DELETE /folders/*, POST /notes/move
- Version bumped to 0.2.0

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/notes/manifest.json

@@ -6,7 +6,7 @@
   "route": "/s/notes",
   "auth": "authenticated",
   "layout": "single",
-  "version": "0.1.0",
+  "version": "0.2.0",
   "icon": "📝",
   "description": "Markdown notes surface with folders, tags, and backlinks.",
   "author": "switchboard",
@@ -20,7 +20,12 @@
     {"method": "PUT",    "path": "/notes/*"},
     {"method": "DELETE", "path": "/notes/*"},
     {"method": "GET",    "path": "/search"},
-    {"method": "GET",    "path": "/stats"}
+    {"method": "GET",    "path": "/stats"},
+    {"method": "GET",    "path": "/folders"},
+    {"method": "POST",   "path": "/folders"},
+    {"method": "PUT",    "path": "/folders/*"},
+    {"method": "DELETE", "path": "/folders/*"},
+    {"method": "POST",   "path": "/notes/move"}
   ],
 
   "db_tables": {
@@ -40,6 +45,18 @@
         ["pinned"],
         ["updated_at"]
       ]
+    },
+    "folders": {
+      "columns": {
+        "name":       "text",
+        "parent_id":  "text",
+        "creator_id": "text",
+        "sort_order":  "int"
+      },
+      "indexes": [
+        ["parent_id"],
+        ["creator_id"]
+      ]
     }
   },