feat(seo): add pre-rendering of home page at build time

[PierreBrisorgueil]

Summary

• What changed: Added a custom Vite plugin that pre-renders configured routes at build time using Puppeteer v24, writing fully rendered HTML to dist/
• Why: SPA crawlers receive an empty HTML shell — pre-rendering ensures search engines and social previews get meaningful content without JavaScript execution
• Related issues: Closes feat(seo): add pre-rendering of home page at build time #3656

Scope

• Modules impacted: src/lib/plugins, src/config/defaults, vite.config.js
• Cross-module impact: none
• Risk level: low — disabled by default, only activates in production with explicit opt-in; gracefully fails without breaking the build

Validation

• npm run lint
• npm run test:unit
• npm run build
• Manual checks done (if applicable)

Guardrails check

• No secrets or credentials introduced (.env*, secrets/**, keys, tokens)
• No risky rename/move of core stack paths
• Changes remain merge-friendly for downstream projects
• Tests added or updated when behavior changed

Notes for reviewers

• Security considerations: Puppeteer is added as a devDependency only — it is not included in the production bundle
• Mergeability considerations: New config key (prerender) is additive; existing configs remain untouched. Plugin is conditionally registered and has no effect when disabled
• Follow-up tasks (optional): Add production config override to enable pre-rendering for deployed environments

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: e1aaa46e-a3ec-4851-a294-e403c23066ef

📥 Commits

Reviewing files that changed from the base of the PR and between ba3da75 and 608bf60.

⛔ Files ignored due to path filters (1)

• package-lock.json is excluded by !**/package-lock.json

📒 Files selected for processing (5)

• package.json
• src/config/defaults/config.development.js
• src/lib/plugins/prerender.js
• src/lib/plugins/tests/prerender.spec.js
• vite.config.js

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch feat/seo-prerender-home

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[codecov]

Codecov Report

❌ Patch coverage is 27.53623% with 50 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.71%. Comparing base (2f2a8ff) to head (608bf60).
⚠️ Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
src/lib/plugins/prerender.js	27.53%	50 Missing ⚠️

❌ Your patch status has failed because the patch coverage (27.53%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3660      +/-   ##
==========================================
- Coverage   98.55%   89.71%   -8.85%     
==========================================
  Files          19       20       +1     
  Lines         485      554      +69     
  Branches      121      133      +12     
==========================================
+ Hits          478      497      +19     
- Misses          7       57      +50     

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[Copilot]

Pull request overview

Adds an opt-in build-time pre-rendering capability to improve SEO for SPA routes by capturing fully-rendered HTML during the Vite production build.

Changes:

• Registers a new Vite build plugin that pre-renders configured routes via Puppeteer and writes HTML files into dist/.
• Adds app.seo.prerender configuration defaults (disabled by default).
• Adds Puppeteer (devDependency) and wires the plugin into vite.config.js.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
vite.config.js	Registers the new prerenderPlugin(appConfig, mode) in the Vite plugins pipeline.
src/lib/plugins/prerender.js	Implements the build-time pre-rendering flow: static server + Puppeteer capture + write to dist/.
src/config/defaults/config.development.js	Introduces app.seo.prerender defaults (disabled, routes list).
package.json	Adds puppeteer to devDependencies.
package-lock.json	Locks the new Puppeteer dependency tree.