Set midday operational shift state for service routing

Stale midday shift flags make alerts route to the wrong on-call team. Update a single shift state so engineers and services have correct context at the noon handoff.

Overview

Remove midday routing ambiguity by writing a single shift state at noon so alerts and handoffs always use the correct context. Implement in minutes to prevent misrouted alerts and ensure on-call engineers have correct information at the noon handoff.