Viral welcome tour + line banner + wall, milestone stepper, rich solo editor, CTA-gated reads

- Welcome tour (3 levels x 10s) unlocks welcome credits; line banner in Profile; public /wall/<username>
- 'Your next move' redesigned as a milestone stepper
- Solo composer: BV-style rich editor (H2/H3, inline image+video, undo/redo, raw text)
- Solo read reward now requires clicking through to the advertiser, not just dwelling
- Sanitizer: inline media whitelist + script/style stripped whole

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

public/view.html

@@ -4,7 +4,7 @@
 <meta charset="utf-8">
 <meta name="viewport" content="width=device-width,initial-scale=1">
 <title>Viewing ad — InstantAdPay</title>
-<link rel="stylesheet" href="/assets/site.css?v=20260905r">
+<link rel="stylesheet" href="/assets/site.css?v=20260905u">
 <style>
   html,body{height:100%;margin:0;overflow:hidden}
   .vw{display:flex;flex-direction:column;height:100vh;height:100dvh;background:var(--bg,#04110c);color:var(--ink,#e8fff7)}
@@ -43,6 +43,6 @@
   </div>
   <iframe class="vframe" id="vFrame" sandbox="allow-scripts allow-same-origin allow-forms allow-popups" referrerpolicy="no-referrer" title="Advertiser site"></iframe>
 </div>
-<script src="/assets/view.js?v=20260905r"></script>
+<script src="/assets/view.js?v=20260905u"></script>
 </body>
 </html>