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.

crates/imap/src/lib.rs

@@ -13,7 +13,7 @@ use imap_proto::{ResponseCode, StatusResponse, protocol::capability::Capability}
 pub mod core;
 pub mod op;
 
-static SERVER_GREETING: &str = "Stalwart IMAP4rev2 at your service.";
+static SERVER_GREETING: &str = concat!(types::brand!(), " IMAP4rev2 at your service.");
 
 pub(crate) static GREETING_WITH_TLS: LazyLock<Vec<u8>> =
     LazyLock::new(|| build_greeting(true, true));