Rebrand to INBUXA: product name, protocol greetings, sign-in page, calendar templates, logos, README

One branding module (types::brand!) supplies the name to every protocol
greeting, the HTTP realm, the startup banner, Received headers, the
user agent, the IMAP ID response and calendar PRODIDs. The sign-in and
calendar pages take ihasmail's palette and font and the INBUXA logo, and
calendar emails embed the INBUXA lockup. Default calendar and address book
names follow. Protocol identifiers (urn:stalwart:jmap, vnd.stalwart Sieve
extensions) and upstream copyright notices are unchanged.

tests/src/imap/basic.rs

@@ -45,7 +45,7 @@ pub async fn test(imap: &mut ImapConnection, _imap_check: &mut ImapConnection) {
     imap.send("ID").await;
     imap.assert_read(Type::Tagged, ResponseType::Ok)
         .await
-        .assert_contains("* ID (\"name\" \"Stalwart\" \"version\" ");
+        .assert_contains("* ID (\"name\" \"INBUXA\" \"version\" ");
 
     // Login should be disabled
     imap.send("LOGIN [email protected] secret").await;