chore: pin all dependencies to exact versions

[John-David Dalton (jdalton)]

Summary

• Pins all dependencies and devDependencies to exact versions (removes ^ ranges)
• This gives us full control over when dependencies get updated
• Dependabot will still open PRs to bump versions so we stay up to date

Test plan

• Verify npm install resolves correctly with pinned versions
• Verify npm run build still works