feed: stop the grid re-sorting ranked feeds chronologically; Trending defaults

The real reason every tab looked identical: VideoListView.render re-sorts
displayVideos by date UNLESS metadata.preserveOrder is set, and only Explore set
it. So For You's tiering, Trending's view-count ranking, and Kids' scoring were
all discarded at render and shown in plain chronological order — i.e. the #21
feed-identity work was invisible. Set preserveOrder for For You, Trending, and
Kids so their feed-engine order survives to the grid.

Also per request:
- Sidebar: Trending now sits above Recently Added.
- Default homepage: logged-out users land on Trending (gated by
  FEATURE_TRENDING_FEED, falls back to Recent); logged-in stays For You. The
  logout-from-For-You redirect follows the same rule.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

components/sidebar.html

@@ -54,15 +54,6 @@
             />
             <span class="sidebar-text">For You</span>
           </a>
-          <a href="#view=most-recent-videos" class="sidebar-nav-link" title="Recently Added">
-            <img
-              src="assets/svg/globe-icon.svg"
-              alt=""
-              aria-hidden="true"
-              class="sidebar-icon"
-            />
-            <span class="sidebar-text">Recently Added</span>
-          </a>
           <a
             id="trendingLink"
             href="#view=trending"
@@ -85,6 +76,15 @@
             </svg>
             <span class="sidebar-text">Trending</span>
           </a>
+          <a href="#view=most-recent-videos" class="sidebar-nav-link" title="Recently Added">
+            <img
+              src="assets/svg/globe-icon.svg"
+              alt=""
+              aria-hidden="true"
+              class="sidebar-icon"
+            />
+            <span class="sidebar-text">Recently Added</span>
+          </a>
           <a href="#view=kids" class="sidebar-nav-link" title="For Kids">
             <svg
               xmlns="http://www.w3.org/2000/svg"