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/lib/env.ts

@@ -0,0 +1,29 @@
+export const env = {
+  OAUTH_PROVIDER: process.env.OAUTH_PROVIDER,
+  OAUTH_CLIENT_ID: process.env.OAUTH_CLIENT_ID,
+  OAUTH_CLIENT_SECRET: process.env.OAUTH_CLIENT_SECRET,
+  OAUTH_AUTHORIZE_URL: process.env.OAUTH_AUTHORIZE_URL,
+  OAUTH_TOKEN_URL: process.env.OAUTH_TOKEN_URL,
+  OAUTH_USERINFO_URL: process.env.OAUTH_USERINFO_URL,
+  OAUTH_ALLOWED_USERS: process.env.OAUTH_ALLOWED_USERS,
+  OAUTH_ALLOWED_ORG: process.env.OAUTH_ALLOWED_ORG,
+  PUBLIC_BASE_URL: process.env.PUBLIC_BASE_URL,
+  GITEA_BASE: process.env.GITEA_BASE,
+  GITEA_OWNER: process.env.GITEA_OWNER,
+  GITEA_REPO: process.env.GITEA_REPO,
+  GITEA_TOKEN: process.env.GITEA_TOKEN,
+  GIT_BRANCH: process.env.GIT_BRANCH || 'main',
+  SESSION_SECRET: process.env.SESSION_SECRET,
+  CSRF_SECRET: process.env.CSRF_SECRET,
+};
+
+export function getBaseUrlFromRequest(req: Request): string {
+  try {
+    if (env.PUBLIC_BASE_URL) return new URL(env.PUBLIC_BASE_URL).toString().replace(/\/$/, '');
+  } catch {}
+  const url = new URL(req.url);
+  url.pathname = '';
+  url.search = '';
+  url.hash = '';
+  return url.toString().replace(/\/$/, '');
+}