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/components/RepoCodeFrequency.vue

@@ -153,7 +153,7 @@ const options: ChartOptions<'line'> = {
           <SvgIcon name="gitea-running" class="tw-mr-2 rotate-clockwise"/>
           {{ locale.loadingInfo }}
         </div>
-        <div v-else class="text red">
+        <div v-else class="tw-text-red">
           <SvgIcon name="octicon-x-circle-fill"/>
           {{ errorText }}
         </div>