added entrypoint for Reticulum in Docker

Replaces static CMD with an entrypoint that generates RNS config from
environment variables (RNS_TCP_HOST/PORT), enabling TCP transport for
environments without LAN auto-discovery (e.g. Docker on macOS).

docker-compose.yml

@@ -6,6 +6,12 @@ services:
     volumes:
       - tinyweb-data:/data
     restart: unless-stopped
+    # Connect to another Reticulum instance over TCP.
+    # Required on macOS (Docker can't do LAN auto-discovery).
+    # On Linux, auto-discovery works with network_mode: host.
+    # environment:
+    #   - RNS_TCP_HOST=10.0.0.100
+    #   - RNS_TCP_PORT=4242
 
 volumes:
   tinyweb-data: