feat(user): allow renaming security keys (webauthn/passkey) (#39413)

Closes https://github.com/go-gitea/gitea/issues/39287

Security key nicknames could only be set at registration, so a skipped
nickname left an auto-generated hex name until the key was
re-registered. Each key now has a Rename button opening a dialog with
the current nickname. A nickname used by another of the user's keys
(case-insensitive) or a blank nickname is rejected. Renames are recorded
as `user:webauth:rename` audit events.

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

tests/e2e/webauthn.test.ts

@@ -5,7 +5,7 @@ const signedIn = /^(?!.*\/user\/(login|webauthn))/; // the target of a finished
 
 async function registerKey(page: Page, nickname: string) {
   await page.goto('/user/settings/security');
-  await page.getByLabel('Nickname').fill(nickname);
+  await page.getByRole('textbox', {name: 'Nickname'}).fill(nickname);
   await page.getByRole('button', {name: 'Add Security Key'}).click();
 }