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.

src/middleware.ts

@@ -0,0 +1,8 @@
+import type { MiddlewareHandler } from 'astro';
+import { getSessionFromRequest } from './lib/session';
+
+export const onRequest: MiddlewareHandler = async (context, next) => {
+  const session = getSessionFromRequest(context.request);
+  (context.locals as any).user = session?.user || null;
+  return next();
+};