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/vite.config.ts

@@ -1,4 +1,3 @@
-import { resolve } from "node:path";
 import { defineConfig } from "vite";
 
 export default defineConfig({
@@ -6,8 +5,9 @@ export default defineConfig({
   build: {
     rollupOptions: {
       input: {
-        main: resolve(__dirname, "index.html"),
-        admin: resolve(__dirname, "admin/index.html"),
+        main: "index.html",
+        admin: "admin/index.html",
+        adminLogin: "admin/login/index.html",
       },
     },
   },