Fix log in button hover/focus feedback

Signed-off-by: Jan C. Borchardt <hey@jancborchardt.net>

core/css/guest.css

@@ -340,7 +340,9 @@ button.primary:not(:disabled):hover,
 button.primary:not(:disabled):focus,
 a.primary:not(:disabled):hover,
 a.primary:not(:disabled):focus {
-	color: rgba(255, 255, 255, .8);
+	color: rgba(255, 255, 255, 1);
+	background-image: linear-gradient(40deg, #0082c9 0%, #30b6ff 100%);
+	background-position: initial;
 }
 
 /* Checkboxes - white only for login */