wrap the admin page in the shared header (with the logout button)
and present the texts entry-point as a card-link in a list-cards
list. the #texts and #logout id hooks used by cypress are
preserved.
add a stylesheet link and the standard responsive viewport meta tag
to every page template. purely additive - no markup or selector
changes - so existing cypress assertions and page js id hooks remain
intact. with this commit every page picks up the base styling from
app.css.
