The Matrix channel had 4 bare except blocks that silently swallowed
transport errors with no logging — stream send/edit failures, media
upload failures, server config fetch failures, and room content send
failures. The Weixin channel had 1 silent state-load failure.
This mirrors commit 98c2f7cc ('fix(weixin): raise exceptions instead
of silently dropping messages') for the Matrix channel and adds a
warning for the remaining silent catch in Weixin's _load_state.
All failures now log at warning level with exc_info=True so operators
can diagnose intermittent Matrix/Weixin transport issues.
