Add Docker deployment setup with health check endpoint

- Add multi-stage Dockerfile with standalone Next.js output
- Add docker-compose.yml with Caddy reverse proxy
- Add nginx configs for local and SSL setups
- Add Caddyfile for automatic HTTPS
- Add docker-entrypoint.sh for runtime config
- Add .env.example and .dockerignore
- Add comprehensive Docker README
- Add /api/health endpoint for container health checks
- Configure next.config.ts for standalone output

docker/Caddyfile

@@ -0,0 +1,40 @@
+# Caddyfile for Synapsis
+# Automatic HTTPS via Let's Encrypt
+
+{$DOMAIN} {
+    # Reverse proxy to Synapsis app
+    reverse_proxy app:3000
+    
+    # Enable compression
+    encode gzip
+    
+    # Security headers
+    header {
+        # Enable HSTS
+        Strict-Transport-Security "max-age=31536000; includeSubDomains; preload"
+        # Prevent clickjacking
+        X-Frame-Options "SAMEORIGIN"
+        # Prevent MIME type sniffing
+        X-Content-Type-Options "nosniff"
+        # XSS protection
+        X-XSS-Protection "1; mode=block"
+        # Referrer policy
+        Referrer-Policy "strict-origin-when-cross-origin"
+    }
+    
+    # Logging
+    log {
+        output file /data/access.log
+        format json
+    }
+    
+    # Increase max body size for uploads (20MB)
+    request_body {
+        max_size 20MB
+    }
+}
+
+# Health check endpoint for Docker
+:8080 {
+    respond /health "healthy" 200
+}