chore: upgrade to React Router 8

[JWThewes]

Summary

• replace react-router-dom 7.x with react-router 8.3.0
• remove the obsolete @types/react-router-dom dependency
• migrate application and test imports to the React Router 8 entry point
• declare the new Node.js minimum of 22.22.0
• regenerate the frontend lockfile

Verification

• npm run typecheck
• npm test (69 files, 452 tests)
• npm run build
• npm run lint
• npm run format:check
• repository pre-commit suite (121 files, 2,411 tests)

This is stacked on #366 and targets feat/enterprise-sso to keep the change isolated from the SSO work.

Closes #373

[jeromevdl]

LGTM