fix: add sirv middleware to serve static assets in production

[MOHIT-SOLANKII]

What does this PR do?

This PR fixes issue #2684, where the "Download assets" button on the /assets page returns a 404 Not Found error in the production environment.

Problem :

The custom Node.js production server (server/main.js) was configured to handle Server-Side Rendering (SSR) via h3 and the SvelteKit node adapter, but it lacked the middleware to serve static files (like assets.zip, images, etc.) that originate from the static/ directory and are copied to build/client during build.

Solution :

• Added sirv : Introduced sirv as a production dependency to efficiently serve static files.
• Updated server/main.js : Added middleware to serve files from the build/client directory before the main SvelteKit handler. This ensures that if a static file exists, it is served; otherwise, the request falls through to the app router.

Test Plan

Verified the fix by running the production server locally (node server/main.js) and confirming that static files (like assets.zip) are correctly served from the build output directory (build/client/) with the correct 200 OK headers.

Related PRs and Issues

Fixes #2684

Have you read the Contributing Guidelines on issues?

Yes

Summary by CodeRabbit

• Chores
  • Improved static asset delivery for the app: files are now served with compression and stronger caching (gzip, ETag, immutable, max-age), reducing load times and bandwidth.
  • Static assets are served earlier in the request flow to improve responsiveness and caching efficiency for end users.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

A new dependency "sirv" (^3.0.2) is added to package.json. In server/main.js, sirv is imported and configured via fromNodeMiddleware to serve static files from build/client at the root path. The middleware is enabled with gzip, etag, maxAge, and immutable options and is mounted before the existing request handler. No exported/public API changes were made.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: adding sirv middleware to serve static assets in production, which directly addresses the core issue.
Linked Issues check	✅ Passed	The PR successfully implements the coding requirements from issue #2684 by adding sirv dependency and configuring static file serving middleware to resolve the 404 error on asset downloads.
Out of Scope Changes check	✅ Passed	All changes are scoped to the stated objective: adding sirv dependency and mounting static middleware. No unrelated modifications detected.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}