Increase Cloud button rollout to 30%

[nadaverell]

Summary

Expand the staged Cloud button rollout from 20% to 30% of eligible Radar installations, increasing exposure while preserving the existing cohort.

What changed

• Raised the compiled Cloud funnel rollout percentage to 30%.
• Existing bucket assignments remain stable, so all previously eligible installations continue to see the button.

Testing

• go test ./internal/server -run "TestCloudFunnel|TestBucket" -count=1
• Visual testing skipped: this changes cohort eligibility only, with no UI or styling changes.