Since v26.07, Instagram is a separate bridge upstream, with its own
binary and its own container image. Both bridges are published to the
same image repository, Instagram's under `ig-`-prefixed tags.

Both roles kept pointing at the unprefixed image, which now carries
only the legacy Instagram code path. That path no longer works against
Instagram's current DM protocol, so mautrix-meta-instagram authenticates
and does its initial sync, then loops on failed MQTT sync tasks and
bridges nothing.

The prefix is derived from `meta_mode`, so it also covers a
mautrix-meta-messenger role run with `meta_mode: instagram`. Renovate
keeps tracking the unprefixed tag for both roles, which is correct:
the two images are built from one git tag.

The self-build checkout took its git ref by parsing the tag out of the
container image reference. That would now ask for a non-existent `ig-`
git tag (upstream has none), and it was already wrong for a commit-hash
pin, where it asked for `HASH-amd64`. It uses `_version` directly now,
like every other role in the playbook does.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/5510

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>