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>

services/markup/renderhelper_issueicontitle_test.go

@@ -26,7 +26,7 @@ func TestRenderHelperIssueIconTitle(t *testing.T) {
 		IssueIndex: 1,
 	})
 	assert.NoError(t, err)
-	assert.Equal(t, `<a href="/link"><span>octicon-issue-opened(16/text green)</span> issue1 (#1)</a>`, string(htm))
+	assert.Equal(t, `<a href="/link"><span>octicon-issue-opened(16/tw-text-green)</span> issue1 (#1)</a>`, string(htm))
 
 	ctx, _ = contexttest.MockContext(t, "/", contexttest.MockContextOption{Render: templates.PageRenderer()})
 	htm, err = renderRepoIssueIconTitle(ctx, markup.RenderIssueIconTitleOptions{
@@ -36,7 +36,7 @@ func TestRenderHelperIssueIconTitle(t *testing.T) {
 		IssueIndex: 1,
 	})
 	assert.NoError(t, err)
-	assert.Equal(t, `<a href="/link"><span>octicon-issue-opened(16/text green)</span> issue1 (user2/repo1#1)</a>`, string(htm))
+	assert.Equal(t, `<a href="/link"><span>octicon-issue-opened(16/tw-text-green)</span> issue1 (user2/repo1#1)</a>`, string(htm))
 
 	ctx, _ = contexttest.MockContext(t, "/", contexttest.MockContextOption{Render: templates.PageRenderer()})
 	_, err = renderRepoIssueIconTitle(ctx, markup.RenderIssueIconTitleOptions{