feat: Handle private.coffee server registration error

Adds a specific link for registration when an error occurs on
the "private.coffee" server, guiding users to a dedicated page
for account creation.

Improves user experience by providing a tailored response
to server-specific conditions.

src/components/structures/auth/Registration.tsx

@@ -640,8 +640,12 @@ export default class Registration extends React.Component<IProps, IState> {
         let errorText;
         const err = this.state.errorText;
         if (err) {
+            if (this.state.matrixClient.baseUrl == "https://matrix.private.coffee") {
+                errorText = <a href="https://register.matrix.private.coffee">Click here to register an account</a>;
+            } else {
                 errorText = <div className="mx_Login_error">{err}</div>;
             }
+        }
 
         let serverDeadSection;
         if (!this.state.serverIsAlive) {