fix: encode dots in URL path segments to prevent browser resolution (#3308)

When editing a regex domain that is just "." (single dot), the browser
interprets it as a relative path component ("current directory") and
resolves it away before sending the request. The server receives an
empty string, causing "Invalid request: Specify item in URI".

This happens because encodeURIComponent(".") returns "." unchanged —
dots are unreserved characters per RFC 3986. The browser only normalizes
literal "." and ".." path segments, not percent-encoded "%2E".

Add utils.encodePathSegment() which wraps encodeURIComponent and also
encodes dots to %2E, then apply it in groups-domains.js (the reported
bug) and groups.js (which was also missing encoding entirely).

Fixes #3308

Signed-off-by: Dominik <dl6er@dl6er.de>

scripts/js/utils.js

@@ -518,6 +518,13 @@ function parseQueryString() {
   return Object.fromEntries(params.entries());
 }
 
+// Encode a string for use as a URL path segment. encodeURIComponent does not
+// encode dots, but browsers resolve "." and ".." as relative path components
+// before sending the request, breaking domains like "." or "..".
+function encodePathSegment(text) {
+  return encodeURIComponent(text).replaceAll(".", "%2E");
+}
+
 function hexEncode(text) {
   if (typeof text !== "string" || text.length === 0) return "";
 
@@ -726,6 +733,7 @@ globalThis.utils = (function () {
     changeTableButtonStates,
     getCSSval,
     parseQueryString,
+    encodePathSegment,
     hexEncode,
     hexDecode,
     listsAlert,