init: static frontend for agency-ai.dev — nginx + YouTube intro video

Static landing page served via nginx 1.27 Alpine container.
Features:
- Fullscreen background image visible from first paint
- YouTube intro video overlay (iframe API, lazy loaded)
- PWA manifest with favicons (48x48, 180x180, 512x512)
- SEO meta tags (OG, Twitter Cards, canonical URL)
- Safety timeout: falls back to static image if YouTube fails

Infrastructure:
- Dockerfile: nginx 1.27 Alpine with custom default.conf
  (gzip, cache headers, security headers X-Frame-Options/nosniff)
- docker-compose.yml: local dev on FRONTEND_PORT (default 8080)
- docker-compose-example/: Dokploy deployment via runtime git clone
  from Gitea, resource limits (256M RAM, 0.5 CPU)

Files:
- index.html: main page with inline CSS + JS (YouTube iframe API)
- default.conf: nginx config (gzip, caching, security headers)
- site.webmanifest: PWA manifest
- assets/imgs/: background image + favicons
- .env.example: FRONTEND_PORT template

Dockerfile

@@ -0,0 +1,19 @@
+FROM nginx:1.27-alpine AS production
+
+# Remove default nginx config
+RUN rm /etc/nginx/conf.d/default.conf
+
+# Copy nginx config from project root
+COPY default.conf /etc/nginx/conf.d/default.conf
+
+# Copy web files (index.html + assets)
+COPY index.html /usr/share/nginx/html/index.html
+COPY site.webmanifest /usr/share/nginx/html/site.webmanifest
+COPY assets/ /usr/share/nginx/html/assets/
+
+EXPOSE 80
+
+HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
+    CMD wget -qO- http://localhost:80/ || exit 1
+
+CMD ["nginx", "-g", "daemon off;"]