fix(auto-update): CI failures on Linux

- Keep the setup result when chown fails. CI runs as a non-root user, where
  chown to the web user raises; that discarded the result file, so the
  General tab would never learn whether setup worked. Regression test added.
- Register the two new /api/v3/system/auto-update routes in the URL map
  snapshot.
- Use utility classes app.css defines (space-y-1, hover:text-red-600).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

test/fixtures/api_v3_url_map.json

@@ -841,6 +841,23 @@
       "POST"
     ]
   ],
+  [
+    "/api/v3/system/auto-update",
+    "api_v3.get_auto_update_status",
+    [
+      "GET",
+      "HEAD",
+      "OPTIONS"
+    ]
+  ],
+  [
+    "/api/v3/system/auto-update/dismiss",
+    "api_v3.dismiss_auto_update_alert",
+    [
+      "OPTIONS",
+      "POST"
+    ]
+  ],
   [
     "/api/v3/system/check-update",
     "api_v3.check_for_update",