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.

.gitignore

@@ -16,6 +16,7 @@ pnpm-debug.log*
 # environment variables
 .env
 .env.production
+.env.local
 
 # macOS-specific files
 .DS_Store