Build WebUI during Vercel deployment and enforce Cache-Control for admin UI

[CJackHwang]

Motivation

• Ensure the WebUI is built as part of Vercel deployments so the static/admin assets are available on each deploy.
• Prevent stale or mismatched admin UI assets and SPA index.html from being served by applying explicit cache semantics at both the application and edge.

Description

• Add a Vercel build command bash scripts/build-webui.sh to vercel.json so Vercel runs the WebUI build during deployment.
• Add Vercel headers rules in vercel.json to set Cache-Control: public, max-age=31536000, immutable for /admin/assets/(.*) and Cache-Control: no-store, must-revalidate for /admin/(.*) at the edge.
• Update routes/home.py to return FileResponse with Cache-Control headers so assets/ files are served with long-term immutable caching and the SPA index.html (and other non-asset static files) are served with no-store, must-revalidate.

Testing

• No automated tests were run for this change.

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Codex Task

[vercel]

Deployment failed with the following error:

If `rewrites`, `redirects`, `headers`, `cleanUrls` or `trailingSlash` are used, then `routes` cannot be present.

Learn More: https://vercel.link/mix-routing-props

[vercel]

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Project	Deployment	Actions	Updated (UTC)
ds2api	Ready	Preview, Comment	Feb 4, 2026 6:20am