UI/allow logo selection (#4982)

# Description of Changes

- Allow switching between logos in-app using the same section in
settings

---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

frontend/src/core/hooks/useLogoAssets.test.ts

@@ -0,0 +1,57 @@
+import { describe, expect, test } from 'vitest';
+import * as fs from 'fs';
+import * as path from 'path';
+import { LOGO_FOLDER_BY_VARIANT } from '@app/constants/logo';
+import type { LogoVariant } from '@app/services/preferencesService';
+
+/**
+ * Tests that all required logo assets exist for each logo variant.
+ * This ensures that when useLogoAssets returns paths, those files actually exist.
+ */
+describe('useLogoAssets - Logo Asset Files', () => {
+  const publicDir = path.resolve(__dirname, '../../../public');
+
+  // All asset files that useLogoAssets references
+  const requiredAssets = [
+    'logo-tooltip.svg',
+    'Firstpage.png',
+    'favicon.ico',
+    'logo192.png',
+    'logo512.png',
+    'StirlingPDFLogoWhiteText.svg',
+    'StirlingPDFLogoBlackText.svg',
+    'StirlingPDFLogoGreyText.svg',
+  ];
+
+  const logoVariants: LogoVariant[] = ['modern', 'classic'];
+
+  describe.each(logoVariants)('%s logo variant', (variant) => {
+    const folder = LOGO_FOLDER_BY_VARIANT[variant];
+    const folderPath = path.join(publicDir, folder);
+
+    test(`folder "${folder}" should exist`, () => {
+      expect(fs.existsSync(folderPath)).toBe(true);
+    });
+
+    test.each(requiredAssets)('should have %s', (assetName) => {
+      const assetPath = path.join(folderPath, assetName);
+      expect(
+        fs.existsSync(assetPath),
+        `Missing asset: ${folder}/${assetName}`
+      ).toBe(true);
+    });
+  });
+
+  describe('manifest files', () => {
+    test('manifest.json should exist for modern variant', () => {
+      const manifestPath = path.join(publicDir, 'manifest.json');
+      expect(fs.existsSync(manifestPath)).toBe(true);
+    });
+
+    test('manifest-classic.json should exist for classic variant', () => {
+      const manifestPath = path.join(publicDir, 'manifest-classic.json');
+      expect(fs.existsSync(manifestPath)).toBe(true);
+    });
+  });
+});
+