Update readme

[bolshakov]

Addresses #894

• Update supported stoplight versions
• Admin read-only mode

[github-actions]

Review price tag

🟢 25 effective lines — about 5–8 min (up from 5 min) of focused review (based on 200–500 lines/hour). This is within the range where reviewers find the most issues per line, and small changes usually receive feedback the fastest.

Why these numbers?

These minutes are what careful defect-finding costs at 200–500 lines/hour — the rate review studies report, not how long a skim takes. "Effective lines" already exclude generated files and lockfiles. Treat the rates and the 200/400 thresholds as guardrails, not laws.