Call the webmail inbuxa-webmail in docs and comments

The webmail repository was renamed from ihasmail-inbuxa to inbuxa-webmail
on 2026-10-05. The OAuth client id stays ihasmail-inbuxa: that is what the
server registers, so the backticked and quoted ids are unchanged.

docs/spec/features/per-domain-directories.md

@@ -412,7 +412,7 @@ check it and the fork keeps it.
 
 ## ihasmail changes
 
-These go in ihasmail-inbuxa, the INBUXA fork of ihasmail, never in public
+These go in inbuxa-webmail, the INBUXA fork of ihasmail, never in public
 ihasmail, which stays Stalwart-facing (SPEC.md §5).
 
 - **Domain editor:** a directory picker offering "server default" and the