Replaces `community.docker.docker_image` with the modern
`docker_image_pull` and `docker_image_build` split modules across all
four task files (synapse, reverse_proxy_companion, goofys,
rust-synapse-compress-state). Drops the `ansible_version` compatibility
ladder and removes four `_container_image_force_pull` variables (the new
pull module handles registry refresh natively via `pull: always`).

The Synapse self-build path uses `ansible.builtin.shell` for BuildKit
support and is left as-is. The customizations image build (which builds
on top of the locally-tagged synapse image) is converted to
`docker_image_build` with `pull: false`, preserving its existing
rebuild-trigger semantics.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/5191.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>