feat: demo deployment with AIUI chat, SSH key auth, Quick Start fix

- Add AIUI pre-built dist to demo/ for Portainer deployment
- Add nginx-demo.conf with Claude API proxy (envsubst for API key)
- Add docker-entrypoint.sh for runtime API key injection
- Update Dockerfile.web to include AIUI and Claude proxy
- Update docker-compose.demo.yml with ANTHROPIC_API_KEY env var
- Switch deploy script from sshpass to SSH key auth
- Fix Quick Start Goals animating before other cards (stagger 5, opacity guard)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

demo/aiui/manifest.webmanifest

@@ -0,0 +1 @@
+{"name":"AIUI","short_name":"AIUI","description":"AI chat interface with rich content surfaces","start_url":"./","display":"standalone","background_color":"#0a0a0a","theme_color":"#0a0a0a","lang":"en","scope":"./","id":"./","display_override":["standalone","minimal-ui"],"orientation":"any","icons":[{"src":"pwa-192x192.png","sizes":"192x192","type":"image/png","purpose":"any"},{"src":"pwa-512x512.png","sizes":"512x512","type":"image/png","purpose":"any"},{"src":"pwa-512x512.png","sizes":"512x512","type":"image/png","purpose":"maskable"}]}