Fix dark mode

Fixes #43.

snikket_web/scss/app.scss

@@ -1046,6 +1046,12 @@ pre.guru-meditation {
 		}
 	}
 
+	body#login {
+		.form-title {
+			color: $primary-800;
+		}
+	}
+
 	body > footer {
 		background-color: $gray-200;
 		color: $gray-800;

snikket_web/scss/invite.scss

@@ -183,3 +183,13 @@ div.form.layout-expanded .lwrap {
 	background-attachment: fixed;
 	background-size: cover;
 }
+
+/* dark mode */
+
+@media (prefers-color-scheme: dark) {
+	div.form.layout-expanded .lwrap {
+		span {
+			background: $gray-200;
+		}
+	}
+}