- Default BIND_SOURCE_IP=false: do not pin inet4_bind_address (stale
source IP after WWAN re-dial was the main rep=0x01 cause).
- Add scripts/watch-cellular.sh: ip monitor events + poll, regenerate
when iface missing or pinned source IP drifts.
- systemd: cellular-proxy-watch.service + 2min timer oneshot fallback.
- cpxy watch {status|once|start|stop|logs}
- Install/upgrade enable watch when ENABLE_CELLULAR_WATCH=true.
WWAN re-dial often keeps iface name (wwan0) but changes private IP.
Stale inet4_bind_address then makes SOCKS rep=0x01 while the panel still
looks healthy. generate/cpxy now re-read live source IP on each regenerate.
Also fix /usr/local/bin/cpxy symlink: dirname($0) became /usr/local and
broke rebind/generate (missing lib.sh).