Refactor content structure and add basic authentication utilities

- Moved event and gallery data to JSON files for cleaner content management.
- Added session management utilities with CSRF protection.
- Integrated OAuth-based login and logout APIs.
- Updated dependencies, including Astro and introduced dotenv-cli.
- Enhanced package.json with local environment support.

astro.config.mjs

@@ -1,5 +1,9 @@
 // @ts-check
 import { defineConfig } from 'astro/config';
+import node from '@astrojs/node';
 
 // https://astro.build/config
-export default defineConfig({});
+export default defineConfig({
+  output: 'server',
+  adapter: node({ mode: 'standalone' }),
+});