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`.

---------

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

templates/repo/issue/sidebar/reviewer_list.tmpl

@@ -82,7 +82,7 @@
 						{{end}}
 					{{end}}
 					<span {{if .Review.TooltipContent}}data-tooltip-content="{{ctx.Locale.Tr .Review.TooltipContent}}"{{end}}>
-						{{svg (printf "octicon-%s" .Review.Type.Icon) 16 (printf "text %s" (.Review.HTMLTypeColorName))}}
+						{{svg (printf "octicon-%s" .Review.Type.Icon) 16 .Review.HTMLTypeColorClass}}
 					</span>
 				</div>
 			</div>
@@ -98,7 +98,7 @@
 				</div>
 				<div class="flex-text-inline">
 					<span {{if .TooltipContent}}data-tooltip-content="{{ctx.Locale.Tr .TooltipContent}}"{{end}}>
-						{{svg (printf "octicon-%s" .Type.Icon) 16 (printf "text %s" (.HTMLTypeColorName))}}
+						{{svg (printf "octicon-%s" .Type.Icon) 16 .HTMLTypeColorClass}}
 					</span>
 				</div>
 			</div>