Improve wg-ui host setup: IP availability checks and current-user install script

- setup-main-host-button: live availability status, grab-next-subnet helper, error/success feedback
- setup-wireguard-host: harden generated shell scripts with set -e
- check-private-ip-address-availability: add user access check, drop manual body validation
- setup-main-host: pass host object with wg_ip_address
- install-wg-ui.sh: run service as the invoking user (root or sudo) instead of a dedicated wgui user, and skip systemd/OpenRC daemon setup when NODE_ENV=development

src/functions/backend/setup/setup-wireguard-host.ts

@@ -82,6 +82,7 @@ export default async function setupWireguardHost({
 
     let pre_sh = ``;
 
+    pre_sh += `set -e\n`;
     pre_sh += `cd ${WIREGUARD_HOST_CONFIG_DIR}\n`;
     pre_sh += `if [ ! -f ${WIREGUARD_PRIVATE_KEY_FILE_NAME} ]; then\n`;
     pre_sh += `    wg genkey | tee ${WIREGUARD_PRIVATE_KEY_FILE_NAME} | wg pubkey > ${WIREGUARD_PUBLIC_KEY_FILE_NAME}\n`;
@@ -112,6 +113,8 @@ export default async function setupWireguardHost({
 
         let sh = ``;
 
+        sh += `set -e\n`;
+
         const POST_UP_PATH = path.join(
             WGUI_LIB_IP_TABLES_DIR,
             `${host_id}-up.sh`,