feat: add admin login page and authentication API

- Created a new login page for admin access at frontend/admin/login/index.html.
- Implemented form submission with error handling for login credentials.
- Updated frontend/index.html to mute the video player and removed unnecessary Alpine.js data binding.
- Enhanced manifest URL resolution in frontend/src/main.ts to include cache-busting parameters.
- Modified vite.config.ts to include the new admin login page in the build process.
- Updated nginx.conf to handle admin login routing, authentication, and API proxying for admin actions.

frontend/index.html

@@ -11,7 +11,7 @@
 </head>
 
 <body class="bg-slate-950 text-slate-200">
-  <div class="flex h-screen" x-data="app()">
+  <div class="flex h-screen">
     <!-- Video Player -->
     <div class="flex-1 flex flex-col">
       <div class="p-4 border-b border-slate-800 flex items-center justify-between bg-slate-900">
@@ -29,7 +29,7 @@
       </div>
 
       <div class="flex-1 flex items-center justify-center p-8 bg-black relative">
-        <video id="player" class="max-h-full rounded-xl shadow-2xl" controls autoplay></video>
+        <video id="player" class="max-h-full rounded-xl shadow-2xl" controls autoplay muted playsinline></video>
         <div id="now-playing-overlay" class="absolute bottom-8 left-8 bg-black/70 backdrop-blur-md px-6 py-3 rounded-2xl text-sm hidden">
           <div class="flex items-center gap-3">
             <div class="text-emerald-400">● LIVE</div>