OAuth Provider Buttons (#5103)

PR to allow other OAuth providers to be displayed on the login screen.
Will show a generic icon when the provider is not in the known set of
providers.
<img width="424" height="205" alt="47ab288dadbc889fd84cc83c9ded0829"
src="https://github.com/user-attachments/assets/2877eb3d-2ade-406f-a2bf-dc404793e30f"
/>

---------

Signed-off-by: dependabot[bot] <[email protected]>
Signed-off-by: stirlingbot[bot] <stirlingbot[bot]@users.noreply.github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Ludy <[email protected]>
Co-authored-by: EthanHealy01 <[email protected]>
Co-authored-by: Ethan <[email protected]>
Co-authored-by: Anthony Stirling <[email protected]>
Co-authored-by: stirlingbot[bot] <195170888+stirlingbot[bot]@users.noreply.github.com>

frontend/src/core/setupTests.ts

@@ -1,6 +1,40 @@
 import '@testing-library/jest-dom';
 import { vi } from 'vitest';
 
+// Mock localStorage for tests
+class LocalStorageMock implements Storage {
+  private store: Record<string, string> = {};
+
+  get length(): number {
+    return Object.keys(this.store).length;
+  }
+
+  clear(): void {
+    this.store = {};
+  }
+
+  getItem(key: string): string | null {
+    return this.store[key] ?? null;
+  }
+
+  key(index: number): string | null {
+    return Object.keys(this.store)[index] ?? null;
+  }
+
+  removeItem(key: string): void {
+    delete this.store[key];
+  }
+
+  setItem(key: string, value: string): void {
+    this.store[key] = value;
+  }
+}
+
+Object.defineProperty(window, 'localStorage', {
+  value: new LocalStorageMock(),
+  writable: true,
+});
+
 // Mock i18next for tests
 vi.mock('react-i18next', () => ({
   useTranslation: () => ({