feat(nextjs): upgrade to 15.5, and refresh config

[avivkeller]

Updates the website to Next.js v15.5, and makes the following configuration changes:

• trailingSlash

  (Ref: https://nextjs.org/docs/app/api-reference/config/next-config-js/trailingSlash)
  "By default Next.js will redirect URLs with trailing slashes to their counterpart without a trailing slash."

• distDir
  We should default to undefined, and let Next.js choose the output directory (so that, in the unlikely event that it changes from .next, we don't need to update this configuration)

• eslint
  No need to specify the directories, when we disable it anyway. (+ next lint is deprecated, so don't reference it in the comment)

• typedRoutes

  (Ref: https://nextjs.org/blog/next-15-5#typed-routes-stable)
  "Typed routes provide compile-time type safety for your application's routes, catching invalid links before they reach production. This feature automatically generates types based on your file structure, ensuring that every <Link> component points to a valid route."

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Project	Deployment	Preview	Updated (UTC)
nodejs-org	Ready	Preview	Aug 20, 2025 11:19pm

[Copilot]

Pull Request Overview

This PR upgrades the Next.js website to version 15.5.0 and modernizes the configuration by removing deprecated or unnecessary options while adding new features like typed routes.

Key changes:

• Upgrade Next.js from 15.4.4 to 15.5.0
• Enable typed routes for compile-time type safety
• Remove deprecated configuration options and simplify ESLint setup

Reviewed Changes

Copilot reviewed 3 out of 5 changed files in this pull request and generated no comments.

File	Description
apps/site/package.json	Updates Next.js and related packages to version 15.5.0
apps/site/next.config.mjs	Removes deprecated options, enables typed routes, and simplifies configuration
apps/site/eslint.config.js	Adds next-env.d.ts to ignored files

Files not reviewed (1)

• pnpm-lock.yaml: Language not supported

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.18%. Comparing base (660f38f) to head (bbb0007).
⚠️ Report is 6 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8096      +/-   ##
==========================================
+ Coverage   73.12%   73.18%   +0.05%     
==========================================
  Files          97       97              
  Lines        8440     8440              
  Branches      229      228       -1     
==========================================
+ Hits         6172     6177       +5     
+ Misses       2267     2262       -5     
  Partials        1        1              

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[github-actions]

Lighthouse Results

URL	Performance	Accessibility	Best Practices	SEO	Report
/en	🟢 91	🟢 100	🟢 100	🟢 100	🔗
/en/about	🟢 99	🟢 97	🟢 100	🟠 88	🔗
/en/about/previous-releases	🟢 98	🟢 93	🟢 100	🟠 89	🔗
/en/download	🟠 85	🟢 100	🟢 100	🟢 100	🔗
/en/blog	🟢 98	🟢 100	🟢 96	🟢 100	🔗