style: improve UI layout and styling

- Increase default window width from 900 to 1200
- Beautify clear button in OrderNumberInput with icon and hover effects
- Simplify ExtractorPage layout by removing collapsible sidebar
- Center settings form controls horizontally in SettingsPage

src/main/index.ts

@@ -15,7 +15,7 @@ dotenv.config({ path: resolve(__dirname, '../../.env') })
 function createWindow(): void {
   // Create the browser window.
   const mainWindow = new BrowserWindow({
-    width: 900,
+    width: 1200,
     height: 670,
     show: false,
     autoHideMenuBar: true,