Fix 30-day availability bar width

[VrianCao]

Summary

• Render the status page availability strip with 30 slots, matching the 30-day uptime data and label.
• Leave the 60-point heartbeat strip unchanged.

Root Cause

MonitorCard requested 60 availability bars while the payload and UI copy are 30-day data, so the component padded the left half with empty slots.

Validation

• pnpm lint
• pnpm typecheck
• pnpm --filter @uptimer/web build
• pnpm test (full suite hit two Worker route timeouts; scoped rerun of those files passed 42/42 tests, then failed only the global coverage threshold because the run was scoped)

Fixes #86