feat(api): extract pure wake-scheduler helpers (nextDailyAfter, recoverScheduleEntry)

Side-effect-free module so missed-wake recovery and rescheduling can be
unit-tested without booting Hono or touching SQLite.

- nextDailyAfter: advances by 24h increments until strictly > now (handles
  multi-day gaps in a single step instead of looping a day at a time).
- recoverScheduleEntry: classifies a past next_wake_at into 'fire now,
  then advance' vs 'silently advance' based on MISSED_WAKE_GRACE_MS (2h).
- CLAUDE_RESET_OFFSET_HOURS / resetHourFor: single source of truth for the
  '+5h reset' display, previously hardcoded in three places.

Includes 12 unit tests covering grace boundaries, multi-day skip, custom
grace windows, and midnight wraparound.

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