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>

templates/repo/issue/view_content/comments.tmpl

@@ -29,7 +29,7 @@
 					<div class="comment-header avatar-content-left-arrow" role="heading" aria-level="3">
 						<div class="comment-header-left">
 							{{if .OriginalAuthor}}
-								<span class="text black tw-font-semibold tw-mr-1">
+								<span class="tw-text-text tw-font-semibold tw-mr-1">
 									{{svg (MigrationIcon $.Repository.GetOriginalURLHostname)}}
 									{{.OriginalAuthor}}
 								</span>
@@ -403,7 +403,7 @@
 								{{end}}
 								<span class="comment-text-line">
 									{{if .OriginalAuthor}}
-										<span class="text black tw-font-semibold">
+										<span class="tw-text-text tw-font-semibold">
 											{{svg (MigrationIcon $.Repository.GetOriginalURLHostname)}}
 											{{.OriginalAuthor}}
 										</span>