fix(brand/ux): real Biz Connect logo, branded loading screen, phone login, no blank gap

- Replace the leftover 'Your Virtual CXO' logo.png with the app icon (C mark) in every
  header (home/index/connect/dashboard) + the app icon on share.html; delete logo.png.
- Loading screen now shows the orbit mark + 'Biz Connect' wordmark + 'Loading…' (was bare).
- Keep the branded splash up until the chat list finishes loading — no blank/stuck gap
  after login (previously hidden before loadSidebar()).
- Login accepts email OR phone (field was type=email, which rejected phone numbers and so
  blocked the mobile-login that triggers the account merge). Label → 'Email or phone'.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/public/share.html

@@ -67,7 +67,7 @@
 <a href="/" id="homeLink" style="position:fixed;top:14px;left:16px;z-index:50;display:inline-flex;align-items:center;gap:6px;background:rgba(255,255,255,.92);color:#1F3B73;text-decoration:none;font-weight:600;font-size:.86rem;padding:.45rem .8rem;border-radius:10px;box-shadow:0 4px 12px rgba(0,0,0,.15)"><span data-ic="arrowLeft" data-sz="16"></span> Home</a>
 <div class="stage">
   <div class="brandpanel">
-    <img src="/logo.png" alt="" style="width:88px;height:88px;border-radius:22px;object-fit:contain;margin-bottom:1.2rem;background:#fff;padding:8px;box-shadow:0 12px 30px rgba(0,0,0,.25)" onerror="this.replaceWith(Object.assign(document.createElement('div'),{className:'mark',textContent:'B'}))">
+    <img src="/icon-512.png" alt="" style="width:88px;height:88px;border-radius:22px;object-fit:contain;margin-bottom:1.2rem;background:#fff;padding:8px;box-shadow:0 12px 30px rgba(0,0,0,.25)" onerror="this.replaceWith(Object.assign(document.createElement('div'),{className:'mark',textContent:'B'}))">
     <div class="wordmark">Biz <span>Connect</span></div>
     <div class="tagline">Secure, instant remote support — no downloads, you stay in control.</div>
   </div>