Add a permanent "Latest" lane beside "Highlights"

Restructure the nav around two permanent lanes, then the reader's chosen ones:
"Highlights" (the curated daily brief — formerly "Today") and "Latest" (the
freshest accepted stories, newest-first). Now that the gate is tight, a
chronological "incoming" feed is safe to expose.

* feed(): new sort="latest" (pure recency) alongside the default best-first
  rank; /api/feed exposes sort=ranked|latest (validated). Still accepted-only
  and boundary-respecting either way.
* lanes.py: two pinned lanes (Highlights + Latest) instead of one.
* Home: "Latest" view + "Load more" pagination for every feed view (offset-
  paged, de-duped). Mobile bottom bar gains a Latest tab.
* LanePicker shows both pinned lanes; nav rail renders them first.

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

frontend/src/lib/components/BottomNav.svelte

@@ -1,14 +1,18 @@
 <script>
-  // Mobile-only primary navigation. Today = the brief, Browse = mood/topic
-  // discovery, You = account + personal controls (shows the user's avatar in).
+  // Mobile-only primary navigation. Highlights = the brief, Latest = the
+  // chronological feed, Browse = mood/topic discovery, You = account.
   import Avatar from './Avatar.svelte';
-  let { active = 'today', onToday, onBrowse, onYou, user = null } = $props();
+  let { active = 'today', onToday, onLatest, onBrowse, onYou, user = null } = $props();
 </script>
 
 <nav class="bottomnav" aria-label="Primary">
   <button class:active={active === 'today'} onclick={onToday}>
     <svg viewBox="0 0 24 24" aria-hidden="true"><circle cx="12" cy="12" r="4.2" fill="none" stroke="currentColor" stroke-width="1.8" /><path d="M12 3v2M12 19v2M3 12h2M19 12h2M5.6 5.6l1.4 1.4M17 17l1.4 1.4M18.4 5.6L17 7M7 17l-1.4 1.4" stroke="currentColor" stroke-width="1.8" stroke-linecap="round" /></svg>
-    <span>Today</span>
+    <span>Highlights</span>
+  </button>
+  <button class:active={active === 'latest'} onclick={onLatest}>
+    <svg viewBox="0 0 24 24" aria-hidden="true"><path d="M4 7h16M4 12h16M4 17h10" fill="none" stroke="currentColor" stroke-width="1.8" stroke-linecap="round" /></svg>
+    <span>Latest</span>
   </button>
   <button class:active={active === 'browse'} onclick={onBrowse}>
     <svg viewBox="0 0 24 24" aria-hidden="true"><circle cx="12" cy="12" r="9" fill="none" stroke="currentColor" stroke-width="1.8" /><path d="M15.5 8.5l-2 5-5 2 2-5 5-2z" fill="none" stroke="currentColor" stroke-width="1.8" stroke-linejoin="round" /></svg>

frontend/src/lib/components/LanePicker.svelte

@@ -26,10 +26,12 @@
 
 {#snippet body()}
   <h2>Your lanes</h2>
-  <p class="sub">Pick the quick-access lanes above the feed. <strong>Today</strong> always stays — choose the rest. Changes apply right away.</p>
+  <p class="sub"><strong>Highlights</strong> and <strong>Latest</strong> always stay — choose the rest. Changes apply right away.</p>
 
   <div class="pinned-row">
-    <span class="chip pinned" title="Always shown">Today <span class="lock">📌</span></span>
+    {#each pool?.pinned ?? [] as p (p.key)}
+      <span class="chip pinned" title="Always shown">{p.label} <span class="lock">📌</span></span>
+    {/each}
   </div>
 
   {#each pool?.groups ?? [] as g (g.name)}