fix(installer): replace confirmation prompt with 5-second countdown

curl | bash pipes stdin so read gets EOF and returns non-zero, which
set -euo pipefail treats as an error and aborts immediately. Replaced
the interactive prompt with a sleep 5 countdown — works whether the
script is piped or run directly.

Bumps version to 0.6.3.

server/src/app.ts

@@ -73,7 +73,7 @@ export async function buildApp() {
 
   fastify.get('/api/health', async () => ({
     status: 'ok',
-    version: '0.6.2',
+    version: '0.6.3',
     timestamp: new Date().toISOString(),
   }))