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/SPEC.md

@@ -618,7 +618,7 @@ the tenant administrators' own view is not yet recorded
 
 ## 8. Open decisions
 
-- The INBUXA fork of ihasmail is **ihasmail-inbuxa** (named 2026-09-18). Open: its repository, and how it tracks
+- The INBUXA fork of ihasmail is **inbuxa-webmail** (named ihasmail-inbuxa on 2026-09-18, renamed 2026-10-05). Open: how it tracks
   public ihasmail (§5).
 - Product name: whether the shipped product is called inbuxa-server or
   something else inside the INBUXA brand.