Refactor code structure for improved readability and maintainability

frontend/admin.html

@@ -4,8 +4,8 @@
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1" />
     <title>Admin · MC Cars</title>
-    <link rel="icon" type="image/png" href="/images/mc-cars-logo.png" />
-    <link rel="apple-touch-icon" href="/images/mc-cars-logo.png" />
+    <link rel="icon" type="image/svg+xml" href="/images/MC-Cars-Logo.svg" />
+    <link rel="apple-touch-icon" href="/images/MC-Cars-Logo.svg" />
     <link href="https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=Playfair+Display:wght@500;600;700&display=swap" rel="stylesheet" />
     <link rel="stylesheet" href="styles.css" />
     <script>document.write('<scr'+'ipt src="config.js?v='+Date.now()+'"><\/scr'+'ipt>')</script>
@@ -17,7 +17,7 @@
     <!-- Login -->
     <section id="loginView" class="admin-login" style="display:none;">
         <div class="logo" style="justify-content:center;margin-bottom:1.5rem;">
-            <span class="logo-mark">MC</span>
+            <img src="/images/MC-Cars-Logo.svg" alt="MC Cars" class="logo-icon" />
             <span>MC Cars Admin</span>
         </div>
         <form id="loginForm" class="admin-form">
@@ -40,7 +40,7 @@
     <!-- Forced password rotation (first login OR user-triggered) -->
     <section id="rotateView" class="admin-login" style="display:none;">
         <div class="logo" style="justify-content:center;margin-bottom:1rem;">
-            <span class="logo-mark">MC</span>
+            <img src="/images/MC-Cars-Logo.svg" alt="MC Cars" class="logo-icon" />
             <span>Passwort setzen</span>
         </div>
         <p style="color:var(--muted);font-size:0.9rem;text-align:center;max-width:38ch;margin:0 auto 1rem;">