Add Profile Selection UI

The logic for handling multiple author profiles exists in popup.js, but the UI in popup.html does not show any buttons to select them. Add a profile selection button group to the popup, as referenced in the documentation.

File to modify: popup.html

How to do it: Add the following block after your title in popup.html:

<!-- ...existing code... -->
<h1>CMT Author Auto-Fill</h1>
<div id="profileButtons">
  <button class="profile-button" data-profile="profile1">Profile 1</button>
  <button class="profile-button" data-profile="profile2">Profile 2</button>
  <button class="profile-button" data-profile="profile3">Profile 3</button>
  <button class="profile-button" data-profile="profile4">Profile 4</button>
</div>
<button type="button" id="autoFillAuthors">Fill Authors</button>
<!-- ...existing code... -->

Update popup.js to handle clicks on these buttons and load the correct profile.