Add QBZ branding icons and logo

- Replace all Tauri icons with QBZ logo variants
- Update LoginView splash screen to use logo.png
- Add logo.png to static folder for web use
- Update favicon.png with QBZ icon

src/lib/components/views/LoginView.svelte

@@ -1,6 +1,5 @@
 <script lang="ts">
   import { invoke } from '@tauri-apps/api/core';
-  import { Music } from 'lucide-svelte';
 
   interface UserInfo {
     userName: string;
@@ -93,7 +92,7 @@
   <div class="login-card">
     <!-- Logo -->
     <div class="logo">
-      <Music size={48} />
+      <img src="/logo.png" alt="QBZ Logo" class="logo-img" />
       <h1>QBZ</h1>
       <p class="subtitle">Native Qobuz Client for Linux</p>
     </div>
@@ -185,6 +184,12 @@
     color: var(--accent-primary);
   }
 
+  .logo-img {
+    width: 80px;
+    height: 80px;
+    object-fit: contain;
+  }
+
   .logo h1 {
     font-size: 32px;
     font-weight: 700;