Use commit instead of author time consistently

Align with radicle explorer and other places where we render the commit
time like the single commit view and commit list

Fixes issue dfa74e83c4f8d0ca903c3f81d278382daad1488a

src/components/CommitActivityItem.svelte

@@ -1,7 +1,7 @@
 <script lang="ts">
   import type { Commit } from "@bindings/repo/Commit";
 
-  import { absoluteTimestamp, formatTimestamp } from "@app/lib/utils";
+  import { commitTimes, formatTimestamp } from "@app/lib/utils";
 
   import Icon from "@app/components/Icon.svelte";
   import Id from "@app/components/Id.svelte";
@@ -13,7 +13,7 @@
 
   const { commit, hideAuthor }: Props = $props();
 
-  const authoredAt = $derived(commit.author.time * 1000);
+  const committedAt = $derived(commit.committer.time * 1000);
 </script>
 
 <style>
@@ -92,8 +92,8 @@
       <div class="meta-hash">
         <Id id={commit.id} clipboard={commit.id} label="commit hash" />
       </div>
-      <div class="timestamp" title={absoluteTimestamp(authoredAt)}>
-        {formatTimestamp(authoredAt)}
+      <div class="timestamp" title={commitTimes(commit)}>
+        {formatTimestamp(committedAt)}
       </div>
     </div>
   </div>