feat(ui): add switch between formats when previewing CITATION.{cff,bib} files (#9103)

See #8222 for context (loosely related to #4595).

## Implemented changes

The conversion logic is kept in the frontend and the related npm libraries are lazy-loaded (unchanged).

### Show some tabs on the preview of the `CITATION.*` file to switch between the formats:

![image](/attachments/be02656f-d906-4191-aa84-d666ee5a90ba)
![image](/attachments/240384e3-dec8-4f02-94e6-261143193541)

### Convert the "Cite repository" to a simple link to the citation file

So that this change can be considered non-breaking

## Current state (before this PR)

The last non-test call of `git.Blob.GetBlobContent` is made to retrieve the content of an eventual CITATION file.
This is available in the `...` menu near the clone URL:
![image](/attachments/ef79128d-ee3f-4e43-a74d-a00e4dcfe6b4)
And is displayed as a popup:

![image](/attachments/7aa930f9-0766-47b9-8145-cbebb5b051b0)

Co-authored-by: 0ko <0ko@noreply.codeberg.org>
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/9103
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Reviewed-by: 0ko <0ko@noreply.codeberg.org>
Co-authored-by: oliverpool <git@olivier.pfad.fr>
Co-committed-by: oliverpool <git@olivier.pfad.fr>

tests/e2e/repo-viewer.test.e2e.ts

@@ -0,0 +1,47 @@
+// Copyright 2025 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// @watch start
+// web_src/js/webcomponents/citation-information.js
+// @watch end
+
+import {expect} from '@playwright/test';
+import {test} from './utils_e2e.ts';
+
+test('CITATION.cff switch', async ({page}) => {
+  const previewPath = '/user2/rendering-test/src/branch/master/CITATION.cff';
+
+  const response = await page.goto(previewPath);
+  expect(response?.status()).toBe(200);
+
+  await expect(page.getByText('cff-version: 1.2.0')).toBeVisible();
+
+  await page.getByRole('button', {name: 'BibTeX'}).click();
+  await expect(page.getByText('cff-version: 1.2.0')).toBeHidden();
+  await expect(
+    page.getByText('howpublished = {https://forgejo.org/},'),
+  ).toBeVisible();
+
+  await page.getByRole('button', {name: 'Citation File Format'}).click();
+  await expect(page.getByText('cff-version: 1.2.0')).toBeVisible();
+});
+
+test('glb file with 3D rendering', async ({page}, workerInfo) => {
+  test.skip(
+    workerInfo.project.name !== 'chromium',
+    'needs some investigation to run on other platforms',
+    // https://codeberg.org/forgejo/forgejo/actions/runs/113344/jobs/3/attempt/1
+  );
+
+  const previewPath =
+    '/user2/rendering-test/src/branch/master/Unicode❤♻Test.glb';
+
+  const response = await page.goto(previewPath);
+  expect(response?.status()).toBe(200);
+
+  await page
+    .getByRole('img', {
+      name: '3D model. Use mouse, touch or arrow keys to move.',
+    })
+    .click();
+});