Keycloak theme for the sign-in and sign-out pages (PD-23, PD-26)

Realm petrolyst's login theme, on Keycloak's unstyled base: a slate panel with the logo and its line
beside the form on a soft card; on a phone a slate band above it; light and dark. Satoshi stays out
of Git by its licence (build.sh). The README adds the install steps. Not deployed.

Bands: none (identity theme).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

keycloak/themes/petrolyst/login/messages/messages_en.properties

@@ -0,0 +1,7 @@
+loginTitle=Sign in to Petrolyst
+loginTitleHtml=
+loginAccountTitle=Sign in to Petrolyst
+doLogIn=Sign in
+logoutConfirmTitle=Log out of Petrolyst
+logoutConfirmHeader=Do you want to log out?
+doLogout=Log out