Idea: bulk delete buckets by host

[jroachgit]

Can we have a way to delete all the buckets under the one host?

[TimeToBuildBob]

This would be useful for cleanup when migrating machines or renaming hosts.

Implementation approach: The Buckets view already groups buckets by hostname. Adding a "Delete all buckets for this host" button per hostname group would be straightforward:

1. The aw-server-rust API already has DELETE /api/0/buckets/{bucket_id} for individual buckets
2. The webui could add a button per host group that calls delete on each bucket under that host
3. A confirmation dialog listing all buckets to be deleted would prevent accidents

The main consideration is that this is a destructive operation — a clear confirmation with the list of buckets (and maybe requiring the user to type the hostname) would be important.

This would be a good candidate to implement after the Vue 3 migration (#772) lands, since the Buckets view will be easier to modify with the updated component architecture.