[ rhonda-rodododo/llamenos ] docs: add Epic 43 (setup wizard), renumber 43-46 → 44-47, make voice optional

New Epic 43: Admin Setup Wizard — guided first-run walkthrough for
channel selection, provider configuration, and basic settings. Lowers
technical barriers by walking admins through setup with connection
tests, provider comparisons, and progressive disclosure.

Key architectural change: telephony/voice is now an optional channel.
The app works with any combination of channels (voice-only, SMS-only,
multi-channel, or reports-only). Updated Epic 42 to include the
https://github.com/rhonda-rodododo/llamenos/commit/7cfb7a0b43c7c292558eb1d26c0903cecb0f451a