Kills the slice-5 placeholder's hardcoded ws://127.0.0.1:8080 Stream URL (routes.rs) — no CPaaS could ever dial it. The webhook now answers with wss://<public-base>/twilio/media-stream derived from the operator's configured base (authority-only; https→wss, http→ws for the dev loop), or 503 when the trunk is unconfigured. config::twilio_credentials existed since slice-5 but was never called: partial/malformed RUTSTER_TWILIO_* config booted silently WebRTC-only. main.rs now fail-fasts at startup, matching every other RUTSTER_* knob. Signed-off-by: Aaron D. Lee <himself@adlee.work>