Add fast iteration tooling

nix run .#fast, .#test and .#webui-dev; see DEVELOPING.md.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AeFqV9dZrK6nipHkPfyM4F

scripts/webui-dev.sh

@@ -0,0 +1,28 @@
+# The web UI on your own machine, with sample settings, leases and your real
+# interface counters. Templates and CSS are re-read on every request: edit,
+# reload the browser. (Pings need root and fail here; applying does nothing.)
+root=$(git rev-parse --show-toplevel)
+dir=$(mktemp -d)
+trap 'rm -rf "$dir"' EXIT
+mkdir -p "$dir/config"
+wan=$(ip -j route show default 2>/dev/null | jq -r '.[0].dev // empty')
+lan=$(ip -j link show 2>/dev/null | jq -r --arg wan "$wan" '[.[] | select(.link_type == "ether" and .ifname != $wan) | .ifname][0] // "eth1"')
+cat > "$dir/config/settings.json" <<JSON
+{"version": 0, "system": {"hostName": "dev"},
+ "router": {"wan": {"interface": "${wan:-eth0}", "ipv4": {"type": "dhcp"}},
+            "lans": {"lan": {"interface": "$lan", "internet": true, "ipv4": {"address": "192.168.10.1"},
+                             "dhcp": {"pool": {"start": "192.168.10.100", "end": "192.168.10.200"}}}}}}
+JSON
+now=$(date +%s)
+cat > "$dir/leases" <<LEASES
+address,hwaddr,client_id,valid_lifetime,expire,subnet_id,fqdn_fwd,fqdn_rev,hostname,state,user_context,pool_id
+192.168.10.101,52:54:00:12:34:56,,3600,$((now + 3000)),1,0,0,laptop,0,,0
+192.168.10.120,52:54:00:aa:bb:cc,,3600,$((now + 1200)),1,0,0,phone,0,,0
+LEASES
+echo '{"version": "0.0.0-dev", "serial": 1, "schema": 0}' > "$dir/router-release"
+cd "$root/pkgs/router-webui"
+echo devpassword1 | go run . passwd "$dir/webui-password"
+echo
+echo "  https://127.0.0.1:8443   password: devpassword1   (the certificate is self-signed)"
+echo
+exec go run . -listen 127.0.0.1:8443 -config "$dir/config" -state "$dir" -leases "$dir/leases" -assets .