v0.37.0

Operator greeting now advertises the voice features, plus public-repo hygiene.

• Greeting — dial-0 now says "Say a room name, or ask for the time, weather,
  directory, or lights," so the voice features (added in 0.33.0) are discoverable
  instead of hidden. Inbound outside calls ring only the cordless by default now
  (inbound_ext example trimmed to a single ext; re-add a second to group-ring).
• Public-readiness (the add-on is open-source): genericized the example
  provider username and caller-ID in the test fixtures to fictional values
  (100000_switchboard, a 555-0100 reserved number) so no real account identifier
  or home phone number ships in the repo; neutralized the shipped default
  cordless_ip (was a real-home address) to empty (device-health auto-follows the
  cordless's registration anyway); hardened .gitignore against accidentally
  committing secrets/state. No secret was ever committed — nothing required
  rotation (verified against full git history).