Gateway /resume rewrites sessions.source to the resuming platform, which is
correct routing behavior (source feeds find_latest_gateway_session_for_peer,
Telegram listings, and the TUI ghost pruner) but destroys creation
provenance. Add a separate immutable created_source column stamped once at
session creation and preserved by all upsert paths; surface it in
hermes sessions list as '<created>→<current>' when the two diverge.
Fixes#56439
f81bb4c485