(docs) Add targeted restore examples

Extend the restore guidance with directory and single-file dry-run
examples so operators can restore a focused path without copying an
entire snapshot.

Render the examples on snapshot detail pages using the selected
snapshot's data path and the host-specific staging destination.

README.md

@@ -181,6 +181,14 @@ restore, use another dry run before writing to the remote root:
 rsync -aHAX --numeric-ids --info=progress2 --dry-run /backups/example.org/scheduled/<snapshot>/data/ root@example.org:/
 ```
 
+For most incidents, prefer a targeted restore instead of copying the whole snapshot. Keep paths relative to the
+snapshot's `data/` directory:
+
+```
+rsync -aHAX --numeric-ids --info=progress2 --dry-run /backups/example.org/scheduled/<snapshot>/data/etc/nginx/ /restore/example.org/etc/nginx/
+rsync -aHAX --numeric-ids --info=progress2 --dry-run /backups/example.org/scheduled/<snapshot>/data/home/example/site/public_html/index.php /restore/example.org/home/example/site/public_html/index.php
+```
+
 Snapshots may use hardlinks for files that are unchanged between backups. That saves disk space and is safe for normal
 restore copies, but do not edit files inside snapshot directories. Treat snapshots as read-only and copy data out with
 rsync.

src/pobsync_backend/templates/pobsync_backend/snapshot_detail.html

@@ -82,6 +82,16 @@
       <div><strong>Restore to staging:</strong></div>
       <pre>{{ restore.local_command }}</pre>
     </div>
+    <div class="stack spaced">
+      <div><strong>Dry-run a directory restore:</strong></div>
+      <pre>{{ restore.partial_dry_run_command }}</pre>
+      <div class="muted">Replace <code>{{ restore.example_relative_path }}</code> with the path you want to restore.</div>
+    </div>
+    <div class="stack spaced">
+      <div><strong>Dry-run a single file restore:</strong></div>
+      <pre>{{ restore.file_dry_run_command }}</pre>
+      <div class="muted">Replace <code>{{ restore.example_file_relative_path }}</code> with the file you want to restore.</div>
+    </div>
     <div class="stack spaced">
       <div><strong>Dry-run restore back to the source host:</strong></div>
       <pre>{{ restore.remote_dry_run_command }}</pre>

src/pobsync_backend/tests/test_views.py

@@ -1427,6 +1427,12 @@ class ViewTests(TestCase):
         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, "Dry-run a directory restore")
+        self.assertContains(response, f"{base.path}/data/etc/nginx/")
+        self.assertContains(response, f"/restore/{host.host}/etc/nginx/")
+        self.assertContains(response, "Dry-run a single file restore")
+        self.assertContains(response, f"{base.path}/data/home/example/site/public_html/index.php")
+        self.assertContains(response, f"/restore/{host.host}/home/example/site/public_html/index.php")
         self.assertContains(response, "Treat snapshot directories as read-only")
         self.assertContains(response, child.dirname)
         self.assertContains(response, f"Run {run.id}")

src/pobsync_backend/views.py

@@ -796,17 +796,27 @@ def _pretty_json(value: object) -> str:
 def _snapshot_restore_guidance(snapshot: SnapshotRecord) -> dict[str, str]:
     source_path = Path(snapshot.path) / "data"
     destination_path = Path("/restore") / snapshot.host.host
+    example_relative_path = Path("etc") / "nginx"
+    example_file_relative_path = Path("home") / "example" / "site" / "public_html" / "index.php"
     quoted_source = _quote_path_with_trailing_slash(source_path)
     quoted_destination = _quote_path_with_trailing_slash(destination_path)
+    quoted_partial_source = _quote_path_with_trailing_slash(source_path / example_relative_path)
+    quoted_partial_destination = _quote_path_with_trailing_slash(destination_path / example_relative_path)
+    quoted_file_source = shlex.quote(str(source_path / example_file_relative_path))
+    quoted_file_destination = shlex.quote(str(destination_path / example_file_relative_path))
     quoted_remote_destination = shlex.quote(f"root@{snapshot.host.address or snapshot.host.host}:/")
     common_args = "rsync -aHAX --numeric-ids --info=progress2"
 
     return {
         "source_path": str(source_path),
         "destination_path": str(destination_path),
+        "example_relative_path": str(example_relative_path),
+        "example_file_relative_path": str(example_file_relative_path),
         "inspect_command": f"ls -la {quoted_source}",
         "dry_run_command": f"{common_args} --dry-run {quoted_source} {quoted_destination}",
         "local_command": f"{common_args} {quoted_source} {quoted_destination}",
+        "partial_dry_run_command": f"{common_args} --dry-run {quoted_partial_source} {quoted_partial_destination}",
+        "file_dry_run_command": f"{common_args} --dry-run {quoted_file_source} {quoted_file_destination}",
         "remote_dry_run_command": f"{common_args} --dry-run {quoted_source} {quoted_remote_destination}",
     }