The template was missing the public_media and direct_media sections, as
well as the bridge.phone_numbers_in_profile, bridge.relay.displayname_format
and backfill.threads.max_initial_messages settings.

Their absence made the bridge fall back to zero values instead of the
defaults that upstream ships (most notably disabling thread backfilling).
The template now matches the configuration that the bridge generates
itself, key for key.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>