Paid shorts: full-screen vertical video feed over the video inventory, earn per watched short

- /shorts page: no-seek full-screen player, server-clock watch, credit + swipe to next
- Reuses /api/my/videos + /api/my/videowatch (same fraud model, daily cap, self-exclusion)
- Linked from Earn credits > Watch videos

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

public/my.html

@@ -394,7 +394,8 @@
           <div class="card">
             <h3>Watch videos, earn credits</h3>
             <p class="muted small">Watch a member's video for its required time and earn credits. The player
-              can't be skipped — the timer runs on our server. You never see your own videos.</p>
+              can't be skipped — the timer runs on our server. You never see your own videos.
+              Prefer a feed? <a href="/shorts">Open Shorts</a> for a full-screen, swipe-to-next experience.</p>
             <p><span class="badge" id="vidProgress">…</span></p>
             <div class="card" style="background:rgba(4,8,7,.5)" id="vidStage">
               <div id="vidBox" class="small muted" style="min-height:120px;display:grid;place-items:center">