Root cause: Yealink AX83H intercepts *0 locally as voicemail access,
never sending it to the SIP server. Fix:
- dialplan.digitmap sends all * codes to server
- DTMF set to RFC2833 for Asterisk ARI compatibility
- Local pickup/voicemail features disabled
- key_as_send enabled for immediate dial
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>