Add getClosingTimeForDate that queries default_hours_scheduled_changes for a pending staged change whose effective_date <= the booking date. Falls back to current working_hours if no staged change applies. Also checks the staged schedule to see if a weekday is closed (returns 00:00).
Extract closing hours check into reusable checkClosingHours helper. Add repo.go for shared DB query helpers. Update admin_reserve to use closing_time and move overlap check inside transaction with FOR UPDATE.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
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