feat: highlight notes created via API with red background

- Add created_via column to notes table (values: 'web' or 'api')
- Mark notes created via POST /api/notes/full as 'api'
- Display light red background for API-created notes in dashboard
- Add "API" badge with lightning icon for visual identification

src/services/NotesService.ts

@@ -29,6 +29,7 @@ export interface Note {
   title: string;
   content: string;
   archived?: boolean;
+  created_via?: 'web' | 'api';
   created_at?: string;
   updated_at?: string;
   todos: Todo[];