feat: Show the build date on the loading banner of unreleased builds (#2659)

tests/utils/build-info.test.ts

@@ -1,6 +1,10 @@
 import { describe, expect, it } from 'vitest';
 
-import { getGitInfo, getReleaseVersion } from '../../src/utils/build-info';
+import {
+  getGitInfo,
+  getReleaseVersion,
+  getUnreleasedBuildDate,
+} from '../../src/utils/build-info';
 
 // As these are running as tests, the won't be build substitutes so this only
 // tests default/fallback values.
@@ -16,3 +20,9 @@ describe('getGitInfo', () => {
     expect(getGitInfo()).toEqual({});
   });
 });
+
+describe('getUnreleasedBuildDate', () => {
+  it('should report no build date for an unbuilt card', () => {
+    expect(getUnreleasedBuildDate()).toBeNull();
+  });
+});