fix(nginx): refactor user ID mapping to improve variable handling

Author: alimd

packages/nginx/etc/nginx/templates/http.d/49-map-auth.conf.template

@@ -1,7 +1,11 @@
 # extract $userIdPrefix from first 3 characters of `$authUserId`
-map $authUserId $userIdPrefix {
+map $authUserId $userIdPrefixTmp {
   default 0;
   # Micro optimization: if `$authUserId` is zero, don't bother with regex.
   0 0;
   "~^(.{3})" $1;
 }
+
+map $userIdPrefixTmp $userIdPrefix {
+  ~^(.*)$ $1;
+}