Issue sidebar and misc css fixes (#15524)

- Replace remaining font icons with SVG in issue sidebar
- Rework issue due date display
- Realign avatar in timeline
- Fix font size in repo search and code explore
- Consolidate active button styles
- Fix loading form on arc-green
- Align time tracker buttons vertically

Fixes: https://github.com/go-gitea/gitea/issues/15896

templates/explore/code.tmpl

@@ -50,7 +50,7 @@
 														<a href="{{EscapePound $repo.HTMLURL}}/src/commit/{{$result.CommitID}}/{{EscapePound $result.Filename}}#L{{.}}"><span>{{.}}</span></a>
 													{{end}}
 												</td>
-												<td class="lines-code"><pre><code class="chroma"><ol class="linenums">{{.FormattedLines | Safe}}</ol></code></pre></td>
+												<td class="lines-code chroma"><code class="code-inner">{{.FormattedLines | Safe}}</code></td>
 											</tr>
 										</tbody>
 									</table>