feat: make SITE_URL and SITE_DOMAIN dynamic via .env and docker compose

- Create .env and .env.example with SITE_DOMAIN=riverrooks.dev and SITE_URL=https://riverrooks.dev
- Migrate src/_data/site.json to src/_data/site.js reading environment variables dynamically
- Update subdomains across Forgejo, CyberChef, Stirling PDF, and Uptime Kuma to inherit site.domain
- Update docker-compose.yml and Dockerfile to accept dynamic SITE_URL and SITE_DOMAIN build args
- Add .env to .gitignore

docker-compose.yml

@@ -5,9 +5,15 @@ services:
     build:
       context: .
       dockerfile: Dockerfile
+      args:
+        SITE_URL: ${SITE_URL:-https://riverrooks.dev}
+        SITE_DOMAIN: ${SITE_DOMAIN:-riverrooks.dev}
     image: river-rooks-blog:latest
     container_name: river_rooks_web
     restart: unless-stopped
+    environment:
+      - SITE_URL=${SITE_URL:-https://riverrooks.dev}
+      - SITE_DOMAIN=${SITE_DOMAIN:-riverrooks.dev}
     ports:
       - "8080:80"
     healthcheck: