ci: run sweepers before/after tests and fix deletion order

[urscale]

The acceptance-test suite sometimes leaves cloud resources behind
(e.g. servers, routers, volumes) when a run timed out or was cancelled.
Subsequent runs then fail because the orphaned resources hit limits
or blocked creation of new dependencies.

Changes:

• Add a pre-test sweep step to clean up leftovers from earlier runs.
• Add a post-test sweep step (always()) so leaks from the current run
  are removed even if the tests fail or timeout.
• Declare missing Sweeper Dependencies so Terraform destroys in the
  correct order: servers before floating IPs, volumes, server groups,
  load balancers, and custom images; routers before networks.

This mirrors the Makefile sweep target that already existed but was
never invoked in CI.