fix: pass commit short hash as version to UI sidebar

Add VITE_APP_VERSION build arg to UI Dockerfile, pass short SHA from
CI docker build step. vite.config.ts truncates to 7 chars so both
CI build and Docker build produce consistent short hashes.

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

ui/vite.config.ts

@@ -7,7 +7,7 @@ const apiTarget = process.env.VITE_API_TARGET || 'http://localhost:8081';
 
 export default defineConfig({
   define: {
-    __APP_VERSION__: JSON.stringify(process.env.VITE_APP_VERSION || 'dev'),
+    __APP_VERSION__: JSON.stringify((process.env.VITE_APP_VERSION || 'dev').slice(0, 7)),
   },
   plugins: [react()],
   server: {