fix(ui): back-to-hosting link + no-F5 backups list

[nechodom]

What

Two backup-flow papercuts reported after the last round of testing.

1. No way back from the job progress page

Starting a backup redirects to /jobs/<id> (progress bar), which only had an All jobs link — no way back to the hosting. Adds a ← Back to <target> button.

JobView::hosting_target() allow-lists the kinds whose target is a single hosting selector (backup, install, migration, restore, hosting_clone, acme_issue, wp_install, profile_apply, …). Cluster / bulk / panel-import jobs carry a label (or nothing) there, so they don't render a dead link to /hostings/<label>.

2. Backups list was stale on return (needed F5)

Coming back to the hosting detail page showed the old list — the new backup only appeared after a manual refresh, because the page was cached.

• Wrapped the backups list in a data-live-refresh="15" region: a running backup flips to ok, and a backup started from the job page shows up on its own.
• The shared refresh driver (base.html) now:
  • fetches with cache: 'no-store' — defeats the stale HTTP cache that forced the F5;
  • force-ticks every live region on bfcache pageshow — the exact back-navigation case. Also benefits Stats + Service health.

Verify

• cargo check -p hyperion-web green (Askama compiles job.hosting_target() + the new region nesting).
• Back link only renders for hosting-scoped job kinds.

Note

main's Cargo.lock is missing ~218 transitive entries (chacha20, cfg_aliases, …) that cargo wants to add — a pre-existing drift, left out of this PR to keep it scoped. Worth a separate chore: sync Cargo.lock if CI ever runs --locked.

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