feat(ui): replace emoji logos with new app icon across dashboard

- NavMenu: swap 🐢 emoji for <img src="logo.png">
- Login page: swap 🎲 emoji for <img src="logo.png">
- Mini App page: swap 🎲 emoji for <img src="logo.png">
- Replace favicon.png with the new logo
- Add logo.png to wwwroot
- Update CSS for .nav-brand-icon, .login-logo, .mini-app-logo to use object-fit: contain sizing

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/GmRelay.Web/Components/Pages/Login.razor

@@ -8,7 +8,7 @@
 
 <div class="login-page">
     <div class="login-card">
-        <div class="login-logo">🎲</div>
+        <img src="logo.png" alt="GM-Relay" class="login-logo" />
         <h1 class="login-title">GM-Relay</h1>
         <p class="login-subtitle">Войдите через Telegram для управления игровыми сессиями</p>
 

src/GmRelay.Web/Components/Pages/MiniApp.razor

@@ -8,7 +8,7 @@
 
 <div class="mini-app-page">
     <div class="mini-app-auth-card" data-auth-status="@miniAppAuthStatus">
-        <div class="mini-app-logo">🎲</div>
+        <img src="logo.png" alt="GM-Relay" class="mini-app-logo" />
         <h1>GM-Relay</h1>
         <p>@statusMessage</p>