feat(desktop-ui): show account avatar image in AI platforms table

Render the account avatarUrl when present, falling back to the initial
letter, with cover sizing inside the avatar circle.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/desktop-client/src/renderer/views/AiPlatformsView.vue

@@ -610,7 +610,13 @@ async function unbindPlatform(account: AccountRow) {
                   class="avatar-circle"
                   :style="{ background: platformMeta(record.platform).accent }"
                 >
-                  <span class="avatar-initial">
+                  <img
+                    v-if="record.avatarUrl"
+                    :src="record.avatarUrl"
+                    :alt="record.displayName"
+                    referrerpolicy="no-referrer"
+                  />
+                  <span v-else class="avatar-initial">
                     {{ record.displayName.slice(0, 1).toUpperCase() }}
                   </span>
                 </span>
@@ -1167,6 +1173,12 @@ async function unbindPlatform(account: AccountRow) {
   box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.05);
 }
 
+.avatar-circle img {
+  width: 100%;
+  height: 100%;
+  object-fit: cover;
+}
+
 .avatar-initial {
   color: #ffffff;
   font-size: 16px;