The sidecar entrypoint hardcoded `udp.mtu: 1472`, the Docker-bridge
IPv4 maximum (1500 MTU - 8 UDP - 20 IPv4 header). Promote it to
`FIPS_UDP_MTU` (defaulting to 1472, preserving behavior) so non-Docker
reuses of the example can override without editing the script. Plumb
the env var through `docker-compose.yml` so a host-level setting
reaches the container, and add a row to the README's env-var table.
Also annotate the static-CI node template with a comment explaining
the same 1472 rationale and the daemon's 1280 default. The template
keeps 1472 as the literal value since the CI suite runs on a Docker
bridge where that's correct.
No behavior change unless the host explicitly sets FIPS_UDP_MTU.
Add a complete example running a strfry Nostr relay exclusively over
the FIPS mesh using the sidecar pattern. Includes Docker Compose
stack, network isolation via iptables, .fips DNS resolution, nak CLI,
build script with cross-compilation support, and documentation.
Also fix the package-openwrt.yml workflow path to match the
openwrt → openwrt-ipk directory rename.