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>
