test(voice): guard route boundary regressions

[CapuchaRojo]

🚀 VetCan Pull Request

Summary

Adds focused regression coverage for the current IVR route boundaries.

This PR verifies:

• Press 4 remains hidden from the public IVR but direct DTMF 4 still routes to hidden staff-controlled reschedule intake.
• Business-hours Press 3 explicit cancellation preserves cancellation intent instead of becoming generic handoff.
• Public reschedule flow does not call rescheduleAppointment by default unless explicitly enabled.

Validation

• WSL npm run build
• targeted voice route tests
• git diff --check

Guardrails

• Tests-first change.
• No payment behavior added.
• No Acuity mutation behavior added.
• No GPT/RAG/LLM behavior added.
• No Press 1, Press 2, veteran, or booking behavior widened.