Fix Dependabot npm update job timeouts

[somethingnew2-0]

Summary

• Pin 19 "latest" deps to semver ranges so Dependabot can correctly classify updates as major vs minor/patch (fixes the empty npm-minor group warning)
• Ignore @rollup/rollup-* platform-specific optional dependencies (16 packages that don't need individual Dependabot PRs)
• Split npm groups into focused families (mui, sentry, react-core, testing, build-tools) so related packages update together in smaller batches

Context

The Dependabot npm update job is timing out at 45 minutes after processing only ~10 of 50+ dependencies. Three root causes:

1. All dependencies land in npm-major because "latest" specifiers give Dependabot no baseline to distinguish major from minor/patch
2. 16 platform-specific @rollup/rollup-* optional deps are checked individually
3. Each dep hits ERESOLVE peer conflicts then retries with --force, doubling processing time

Test plan

• npm ls confirms lockfile is valid with the new specifiers (all pinned ranges match installed versions)
• Monitor next Dependabot run to confirm job completes within timeout
• Verify the npm-minor group warning no longer appears
• Verify separate, smaller PRs are created per group