ci: increase test timeout to 15 minutes

Network-dependent tests like test_refresh_joined_group need more time
in CI environments due to peer discovery and file replication delays

Author: tripledoublev

.github/workflows/lint_and_test.yml

@@ -27,6 +27,7 @@ jobs:
   test:
     needs: lint
     runs-on: ubuntu-latest
+    timeout-minutes: 15
     strategy:
       matrix:
         test_name: [