fix: use 24-hour days for AM startup log rotation

[robjarawan]

Summary

• use 86,400 seconds for the day threshold and divisor in the AM child startup logging helper
• align cfglogs() with the already-correct normal instance logging path
• verify exact handler arguments for 12h, 1d, and 2d using deterministic constructor mocks

Scope is intentionally limited: this corrects the short-lived AM child startup handler. It does not claim that running workers previously retained a two-day rotation cadence.

Tests

• cfglogs interval regression — 3 passed
• pytest -q tests/sarracenia/config_test.py — 19 passed
• available repository suite — 299 passed, 2 skipped
• compile, diff, and 119-character checks passed

Closes #36.

[github-actions]

Test Results

377 tests   375 ✅  1m 30s ⏱️
  1 suites    1 💤
  1 files      1 ❌

For more details on these failures, see this check.

Results for commit a597c23.