With share_instance = Yes, announces weren't being sent over TCP
in Docker environments. Setting it to No ensures each TinyWeb
instance manages its own Reticulum interfaces directly.
New TinyWeb instances now auto-connect to rnode.bre.land:4242
so users get internet mesh connectivity out of the box without any
manual Reticulum configuration. Env var overrides still supported.
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).
