feat: ask VPN client subnet at install (SERVER_WG_IPV4_NETWORK)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

server/secondary-setup.sh

@@ -18,7 +18,23 @@ MAIN_API_KEY="${MAIN_API_KEY:?Set MAIN_API_KEY=your_api_key}"
 MAIN_PROTO="${MAIN_PROTO:-http}"
 MAIN_PORT="${MAIN_PORT:-8443}"
 OBF_PORTS="${OBF_PORTS:-2083,5443,993}"
+# Подсеть клиентов: env SERVER_WG_IPV4_NETWORK или вопрос в терминале (Enter = 10.25.0.0/16)
+if [ -z "${SERVER_WG_IPV4_NETWORK:-}" ] && [ -r /dev/tty ] && [ -t 1 ]; then
+    printf 'Подсеть VPN-клиентов [10.25.0.0/16]: ' > /dev/tty
+    read -r -t 60 SERVER_WG_IPV4_NETWORK < /dev/tty || true
+fi
 SERVER_WG_IPV4_NETWORK="${SERVER_WG_IPV4_NETWORK:-10.25.0.0/16}"
+SERVER_WG_IPV4_NETWORK="$(python3 - "$SERVER_WG_IPV4_NETWORK" <<'PY'
+import ipaddress, sys
+try:
+    net = ipaddress.ip_network(sys.argv[1].strip(), strict=False)
+except ValueError:
+    sys.exit("ERROR: bad subnet " + sys.argv[1])
+if net.version != 4 or not net.is_private or net.prefixlen > 29:
+    sys.exit("ERROR: subnet must be private IPv4, /8../29 (e.g. 10.25.1.0/24)")
+print(net)
+PY
+)" || exit 1
 PHOBOS_DIR="/opt/Phobos"
 WG_SERVER_IPV4="$(python3 - "$SERVER_WG_IPV4_NETWORK" <<'PY'
 import ipaddress, sys