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

@@ -2,7 +2,8 @@ FROM node:20-alpine AS build
 
 WORKDIR /app
 COPY package*.json ./
-RUN npm ci
+# Fallback to npm install if no lockfile is present
+RUN npm ci || npm install
 COPY . .
 # Ensure CSS variables are present
 RUN mkdir -p public/styles
@@ -16,7 +17,8 @@ RUN npm install -g serve
 COPY --from=build /app/dist ./dist
 
 EXPOSE 3000
-CMD ["serve", "-s", "dist", "-l", "3000"]
+# Serve static files (no SPA fallback), so /admin serves dist/admin/index.html
+CMD ["serve", "-l", "3000", "dist"]
 
 HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
   CMD wget -qO- http://localhost:3000/ || exit 1