Add version number display to UI header

Inject app version (v1.0.0) at build time via Vite define config
and display it below the title in muted text.

app/src/App.tsx

@@ -102,9 +102,10 @@ function App() {
           />
         </>
       )}
-      <h1 style={{ fontSize: '20px', marginBottom: '12px', color: '#111' }}>
+      <h1 style={{ fontSize: '20px', marginBottom: '2px', color: '#111' }}>
         EMBA Specialization Solver
       </h1>
+      <div style={{ fontSize: '11px', color: '#999', marginBottom: '12px' }}>v{__APP_VERSION__}</div>
 
       <ModeToggle mode={state.mode} onSetMode={setMode} />
 

app/src/vite-env.d.ts

@@ -0,0 +1,3 @@
+/// <reference types="vite/client" />
+
+declare const __APP_VERSION__: string;

app/vite.config.ts

@@ -5,6 +5,9 @@ import react from '@vitejs/plugin-react'
 // https://vite.dev/config/
 export default defineConfig({
   plugins: [react()],
+  define: {
+    __APP_VERSION__: JSON.stringify('1.0.0'),
+  },
   server: {
     allowedHosts: ['soos'],
   },