feat(auth): add login/logout, user identity, and soft auth gate
- api/logout.php: destroys session + clears cookie, redirects to /
- api/guest-session.php: sets guest flag, lets users explore without account
- layout.php: removes hard PHP redirect; authenticated users see email +
"Logg ut" in topbar; guests see guest banner (sticky, dismissible) and
auth gate modal (dismissible via localStorage) instead of redirect
- layout_footer.php: injects auth gate modal + JS for banner/modal dismiss
- layout_dashboard.php: adds username + "Logg ut" to dash-topbar
- index.php: adds "Utforsk uten konto" link under primary login CTA
- tools.css: .guest-banner, .auth-gate-*, .topbar-user, .dash-topbar__user
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
daveadmin
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