ui(bb): update post list surface colors

src/routes/idaa/(idaa)/bb/ae_idaa_comp__post_obj_li.svelte

@@ -105,7 +105,7 @@
                             {@html idaa_post_obj.content}
                             <!-- Add an overlay to fade the content out when close to max height -->
                             <div
-                                class="post__content__fade w-full h-16 absolute bottom-0 left-0 bg-linear-to-t from-white to-transparent"
+                                class="post__content__fade w-full h-16 absolute bottom-0 left-0 bg-linear-to-t from-surface-50 to-transparent"
                             ></div>
                         </div>
                     {/if}