Refactor text utility classes to Tailwind CSS (#36703)

Replace Fomantic/custom CSS text utility classes with their Tailwind
equivalents:

- `.text.<color>` compound classes → `tw-text-<color>` classes
- `.text.small` (`font-size: 0.75em`) → `tw-text-xs` (11px)
- `.text.truncate` (`overflow-x: hidden; text-overflow: ellipsis;
white-space: nowrap; display: inline-block`) → `tw-inline-block
tw-truncate`

Remove the now-unused CSS rules from `base.css` and `dashboard.css`.

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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

web_src/js/features/repo-issue-content.ts

@@ -20,7 +20,7 @@ function showContentHistoryDetail(issueBaseUrl: string, commentId: string, histo
       ${i18nTextOptions}
       ${svg('octicon-triangle-down', 14, 'dropdown icon')}
       <div class="menu">
-        <div class="item red text" data-option-item="delete">${i18nTextDeleteFromHistory}</div>
+        <div class="item tw-text-red" data-option-item="delete">${i18nTextDeleteFromHistory}</div>
       </div>
     </div>
   </div>