fix(e2e): resolve SPA auth race conditions in Robot tests

- Rework Login As Admin: use sessionStorage flag + relative fetch login + polling loop
- Add data-testid to JailDetailPage error render path
- Add Collections library import for Get From List keyword
- Fix /jails API response extraction (returns {items, total} not plain list)
- Change Close Context to Close Browser for proper browser cleanup
- Add domcontentloaded + Sleep + polling to Config test to avoid premature timeout

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

e2e/resources/common.resource

@@ -2,8 +2,6 @@
 Library    Browser
 Library    RequestsLibrary
 
-Variables    ${CURDIR}/../../.env
-
 *** Variables ***
 ${FRONTEND_URL}    http://localhost:5173
 ${BACKEND_URL}     http://localhost:8000