Fixing the background color of the "re-login" screen when your session has timed out. (#18284)

* Updated modal background color

The background color of the authentication modal has been updated to use a CSS variable for better customization. The default value remains the same.

* Update umb-app-auth-modal.element.ts to use less specific css custom property

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Co-authored-by: Niels Lyngsø <[email protected]>

Author: readingdancer

src/Umbraco.Web.UI.Client/src/packages/core/auth/modals/umb-app-auth-modal.element.ts

@@ -170,7 +170,7 @@ export class UmbAppAuthModalElement extends UmbModalBaseElement<UmbModalAppAuthC
 		css`
 			:host {
 				display: block;
-				background: rgb(244, 244, 244);
+				background: var(--uui-color-surface, #f4f4f4);
 
 				--curves-color: var(--umb-login-curves-color, #f5c1bc);
 				--curves-display: var(--umb-login-curves-display, inline);