Add CMS features with admin interface and OAuth authentication integration

- Introduced Caddy server for serving frontend and API backend.
- Implemented admin dashboard for creating, editing, and managing events.
- Replaced session-based authentication with token-based OAuth using Gitea.
- Added support for drag-and-drop event reordering in the admin interface.
- Standardized Fastify route validation with JSON schemas.
- Enhanced authentication flow with cookie-based state and secure token storage.
- Reworked backend routes to handle publishing, event management, and content updates.
- Updated `Dockerfile.caddy` and `fly.toml` for deployment configuration.

Dockerfile.caddy

@@ -0,0 +1,9 @@
+FROM caddy:2-alpine
+
+# Embed Caddyfile directly to avoid host path issues on Windows
+RUN mkdir -p /etc/caddy \
+ && printf ":80\nlog\nroute {\n  handle /api/* {\n    reverse_proxy backend:8080\n  }\n  handle {\n    reverse_proxy frontend:3000\n  }\n}\n" > /etc/caddy/Caddyfile
+
+EXPOSE 80
+
+CMD ["caddy", "run", "--config", "/etc/caddy/Caddyfile", "--adapter", "caddyfile"]