Migrate UI shell from Vue to React (#61)

* feat: start React UI migration

* chore: remove Vue build stack

* refactor: organize React app structure

* fix: restore ribbon tab content

* feat: use shadcn tabs for ribbon

---------

Co-authored-by: Sia <me@siamand.cc>

Author: code-by-sia

README.md

@@ -49,7 +49,7 @@ npm install
 Start the development server:
 
 ```sh
-npm run serve
+npm run dev
 ```
 
 Build for production:
@@ -58,16 +58,16 @@ Build for production:
 npm run build
 ```
 
-Run linting:
+Run type checking:
 
 ```sh
-npm run lint
+npm run typecheck
 ```
 
 Run unit tests:
 
 ```sh
-npm run test:unit
+npm test
 ```
 
 ## Documentation

babel.config.js

@@ -2,7 +2,7 @@
 
 ## High-Level Components
 
-- UI Layer (currently Vue-based)
+- UI Layer (React-based)
 - Spreadsheet core logic
 - Canvas renderer
 - Formula evaluation
@@ -17,4 +17,4 @@
 
 ## Future Direction
 
-A future React migration should focus on the UI layer only while preserving the existing spreadsheet core.
+A future React migration should focus on the UI layer only while preserving the existing spreadsheet core.