(ui) Clarify destructive action flows

Make retention apply, incomplete cleanup, and SSH key deletion visibly
destructive with warning copy, danger styling, and consistent cancel actions
while keeping the existing confirmation requirements intact.

Refs #25

src/pobsync_backend/templates/pobsync_backend/retention_plan.html

@@ -104,8 +104,12 @@
   </section>
 
   {% if plan.delete %}
-    <section class="panel">
+    <section class="panel highlight warning">
       <h2>Apply Retention</h2>
+      <p class="muted">
+        This permanently deletes the snapshot directories listed in Would Delete. Confirm the host and delete count
+        before applying the plan.
+      </p>
       <form method="post" action="{% url 'apply_host_retention' host.host %}" class="form-grid">
         {% csrf_token %}
         {{ apply_form.non_field_errors }}
@@ -138,8 +142,9 @@
           <div class="helptext">{{ apply_form.confirm_delete_count.help_text }}</div>
         </div>
 
-        <div class="actions">
-          <button type="submit">Apply retention</button>
+        <div class="form-actions">
+          <button type="submit" class="danger">Apply retention</button>
+          <a class="button-link secondary" href="{% url 'host_retention_plan' host.host %}?kind={{ kind }}">Cancel</a>
         </div>
       </form>
     </section>
@@ -200,6 +205,10 @@
       </table>
 
       <h3>Cleanup Incomplete Snapshots</h3>
+      <p class="muted">
+        This deletes only incomplete snapshot directories and their tracking records. Successful manual and scheduled
+        snapshots are not touched.
+      </p>
       <form method="post" action="{% url 'cleanup_host_incomplete_snapshots' host.host %}" class="form-grid">
         {% csrf_token %}
         {{ incomplete_cleanup_form.non_field_errors }}
@@ -225,8 +234,9 @@
           <div class="helptext">{{ incomplete_cleanup_form.confirm_delete_count.help_text }}</div>
         </div>
 
-        <div class="actions">
-          <button type="submit">Delete incomplete snapshots</button>
+        <div class="form-actions">
+          <button type="submit" class="danger">Delete incomplete snapshots</button>
+          <a class="button-link secondary" href="{% url 'host_retention_plan' host.host %}?kind={{ kind }}">Cancel</a>
         </div>
       </form>
     </section>

src/pobsync_backend/templates/pobsync_backend/ssh_credential_form.html

@@ -67,6 +67,7 @@
         </div>
         <div class="form-actions">
           <button type="submit" class="danger" {% if credential.hosts.exists or credential.global_configs.exists %}disabled{% endif %}>Delete SSH key</button>
+          <a class="button-link secondary" href="{% url 'ssh_credentials' %}">Cancel</a>
         </div>
       </form>
     </section>

src/pobsync_backend/tests/test_views.py

@@ -554,6 +554,8 @@ class ViewTests(TestCase):
             self.assertEqual(response.status_code, 200)
             self.assertContains(response, "Cancel")
             self.assertContains(response, reverse("ssh_credentials"))
+        self.assertContains(edit_response, "Delete SSH key")
+        self.assertContains(edit_response, 'class="danger"', html=False)
 
     def test_ssh_credentials_view_generates_filesystem_key(self) -> None:
         self.client.force_login(self.staff_user)
@@ -1835,6 +1837,9 @@ class ViewTests(TestCase):
         self.assertNotContains(response, "<div class=\"label\">Source</div>", html=True)
         self.assertContains(response, "Confirm delete count")
         self.assertContains(response, "Type 1 to confirm the current number of planned deletions.")
+        self.assertContains(response, "This permanently deletes the snapshot directories listed in Would Delete.")
+        self.assertContains(response, 'class="danger"', html=False)
+        self.assertContains(response, "Cancel")
 
     def test_retention_plan_warns_when_scheduled_prune_limit_is_exceeded(self) -> None:
         self.client.force_login(self.staff_user)
@@ -1910,6 +1915,8 @@ class ViewTests(TestCase):
         self.assertContains(response, "excluded from retention cleanup")
         self.assertContains(response, "Delete incomplete snapshots")
         self.assertContains(response, "Type 1 to confirm the current number of incomplete snapshots.")
+        self.assertContains(response, "This deletes only incomplete snapshot directories")
+        self.assertContains(response, 'class="danger"', html=False)
 
     def test_incomplete_cleanup_deletes_incomplete_snapshot_after_confirmation(self) -> None:
         self.client.force_login(self.staff_user)