feat(report): display block range and verbose gas in load test summary

[kmchicoine]

Summary

• Display block range (first → last) with block count in the load test summary section
• Format gas values verbosely ("million gas/s" instead of "Mgas/s") for avg gas/s and total gas
• Update page title to "Base Load Tests"

[cb-heimdall]

✅ Heimdall Review Status

Requirement	Status	More Info
Reviews	✅ 1/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1