Prep for the RC1 release of the desktop app

frontend/src/components/window/MainWindow.svelte

@@ -4,10 +4,12 @@
 	import type { AppWindowState } from "@graphite/state-providers/app-window";
 	import type { DialogState } from "@graphite/state-providers/dialog";
 	import type { TooltipState } from "@graphite/state-providers/tooltip";
+	import { isDesktop } from "@graphite/utility-functions/platform";
 
 	import Dialog from "@graphite/components/floating-menus/Dialog.svelte";
 	import Tooltip from "@graphite/components/floating-menus/Tooltip.svelte";
 	import LayoutCol from "@graphite/components/layout/LayoutCol.svelte";
+	import TextLabel from "@graphite/components/widgets/labels/TextLabel.svelte";
 	import StatusBar from "@graphite/components/window/status-bar/StatusBar.svelte";
 	import TitleBar from "@graphite/components/window/title-bar/TitleBar.svelte";
 	import Workspace from "@graphite/components/window/workspace/Workspace.svelte";
@@ -29,6 +31,17 @@
 	{#if $tooltip.visible}
 		<Tooltip />
 	{/if}
+	{#if isDesktop() && new Date() > new Date("2026-01-31")}
+		<LayoutCol class="release-candidate-expiry">
+			<TextLabel>
+				<p>
+					This is an outdated desktop release candidate build. Its testing<br />
+					period has concluded and the next build is available for download.<br />
+					Please update to help us continue testing by reporting new issues.
+				</p>
+			</TextLabel>
+		</LayoutCol>
+	{/if}
 </LayoutCol>
 
 <style lang="scss" global>
@@ -37,4 +50,24 @@
 		overflow: auto;
 		touch-action: none;
 	}
+
+	.release-candidate-expiry {
+		position: absolute;
+		top: 50%;
+		left: 50%;
+		transform: translate(-50%, -50%);
+		background-color: var(--color-e-nearwhite);
+		color: var(--color-2-mildblack);
+		opacity: 0.9;
+		pointer-events: none;
+		padding: 12px 40px;
+		border-radius: 4px;
+		text-align-last: justify;
+		font-size: 18px;
+		z-index: 1000;
+
+		.text-label {
+			line-height: 1.5;
+		}
+	}
 </style>