Upgrade webpack-dev-server 5.2.6 → 6.0.0

[n-lark]

Upgrade webpack-dev-server 5.2.6 → 6.0.0 (major)

Dependabot PR #7754. Dev dependency (devDependencies, currently ^5.2.1, lockfile 5.2.5); powers the local npm run serve dev server only, not shipped to production. Pulled out of the weekly Dependabot slot per the major-version process — needs an owner and verification, not a batch merge.

Compatibility pre-check

• ✅ Node: v6 requires >= 22.15.0; dev-only tool and the dev/CI default is Node 24, which satisfies it. Shipped engines: >=20.10.0 is unaffected (not a runtime dep). Ensure CI build lanes run Node ≥ 22.15.
• ✅ webpack: v6 peer ^5.101.0; installed webpack 5.108.4 satisfies it.
• ✅ webpack-cli: installed 7.2.1; v6 removes built-in CLI flags in favor of webpack-cli serve (already used).

Breaking changes to review

• Drops Node.js < 22.15.0.
• Bumps webpack peer from ^5.0.0 to ^5.101.0.
• Removes CLI flags — use the serve command from webpack-cli.
• Removes the bypass proxy option.
• Removes internalIP/internalIPSync static methods on Server.
• Drops SockJS: webSocketServer no longer accepts 'sockjs'.
• Removes spdy; HTTP/2 now via Node node:http2.
• Express 5, http-proxy-middleware v4, webpack-dev-middleware v8 (getFilenameFromUrl() now async).
• Our config uses only devServer.port and historyApiFallback — neither is listed as changed; to confirm from changelog.

To do before merge

• Verify npm run serve (dev server) still boots and HMR works.
• Reconcile any renamed/removed devServer options with our config.
• Read the 6.x migration guide.

Refs

• Branch: dependabot/npm_and_yarn/webpack-dev-server-6.0.0
• PR: build(deps-dev): bump webpack-dev-server from 5.2.6 to 6.0.0 #7754
• Upstream: https://github.com/webpack/webpack-dev-server/releases/tag/v6.0.0