feat(bash): prompt for PostgreSQL (#4472)

* feat(install): prompt for SQLite vs PostgreSQL during install

* fix(install): write env file to per-distro path and handle pg-install failure

The env file was hardcoded to /etc/default/x-ui, but RHEL/Fedora units read
/etc/sysconfig/x-ui, Arch reads /etc/conf.d/x-ui, and Alpine OpenRC auto-
sources /etc/conf.d/x-ui. PostgreSQL selection was silently dropped on every
distro except Debian. Also initdb on openSUSE (service wouldn't start) and
prompt the operator on local-install failure instead of silently demoting
to SQLite.

* fix(scripts): make x-ui.sh and update.sh PostgreSQL-aware

update.sh ran setting -show and migrate without sourcing the env file, so
PostgreSQL users had migrations applied to the SQLite default and settings
introspection read the wrong DB. Sourcing the per-distro env file at the
start of update_x-ui exports XUI_DB_TYPE/XUI_DB_DSN to all binary calls.

x-ui.sh now shows the active backend in View Current Settings (password
masked) and removes the env file on uninstall so a later reinstall doesn't
inherit a stale DSN.

x-ui.sh

@@ -179,6 +179,20 @@ delete_script() {
     exit 1
 }
 
+xui_env_file_path() {
+    case "${release}" in
+        ubuntu | debian | armbian)
+            echo "/etc/default/x-ui"
+            ;;
+        arch | manjaro | parch | alpine)
+            echo "/etc/conf.d/x-ui"
+            ;;
+        *)
+            echo "/etc/sysconfig/x-ui"
+            ;;
+    esac
+}
+
 uninstall() {
     confirm "Are you sure you want to uninstall the panel? xray will also uninstalled!" "n"
     if [[ $? != 0 ]]; then
@@ -202,6 +216,7 @@ uninstall() {
 
     rm /etc/x-ui/ -rf
     rm ${xui_folder}/ -rf
+    rm -f "$(xui_env_file_path)"
 
     echo ""
     echo -e "Uninstalled Successfully.\n"
@@ -289,6 +304,18 @@ check_config() {
     fi
     LOGI "${info}"
 
+    local db_env_file
+    db_env_file="$(xui_env_file_path)"
+    if [[ -r "$db_env_file" ]] && grep -q '^XUI_DB_TYPE=postgres' "$db_env_file"; then
+        local dsn
+        dsn="$(grep -E '^XUI_DB_DSN=' "$db_env_file" | head -1 | cut -d= -f2-)"
+        local dsn_safe
+        dsn_safe="$(echo "$dsn" | sed -E 's|(://[^:/@]+:)[^@]+@|\1****@|')"
+        echo -e "${green}Database: PostgreSQL — ${dsn_safe}${plain}"
+    else
+        echo -e "${green}Database: SQLite (/etc/x-ui/x-ui.db)${plain}"
+    fi
+
     local existing_webBasePath=$(echo "$info" | grep -Eo 'webBasePath: .+' | awk '{print $2}')
     local existing_port=$(echo "$info" | grep -Eo 'port: .+' | awk '{print $2}')
     local existing_cert=$(${xui_folder}/x-ui setting -getCert true | grep 'cert:' | awk -F': ' '{print $2}' | tr -d '[:space:]')