(docs) Add manual restore guidance for snapshots

Document the manual restore workflow in the README and surface snapshot-
specific restore commands on the snapshot detail page.

The guidance keeps restores intentionally manual for now: inspect the
snapshot data directory, run rsync with --dry-run, restore to staging
first, and treat hardlinked snapshot files as read-only.

src/pobsync_backend/tests/test_views.py

@@ -1421,6 +1421,13 @@ class ViewTests(TestCase):
         self.assertContains(response, "Stats")
         self.assertContains(response, "Files seen:</strong> 100")
         self.assertContains(response, "Hardlinked files:</strong> 9")
+        self.assertContains(response, "Restore Guidance")
+        self.assertContains(response, f"{base.path}/data")
+        self.assertContains(response, f"/restore/{host.host}")
+        self.assertContains(response, "rsync -aHAX --numeric-ids --info=progress2 --dry-run")
+        self.assertContains(response, f"{base.path}/data/")
+        self.assertContains(response, "root@web-01.example.test:/")
+        self.assertContains(response, "Treat snapshot directories as read-only")
         self.assertContains(response, child.dirname)
         self.assertContains(response, f"Run {run.id}")
         self.assertContains(response, reverse("run_detail", args=[run.id]))