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/email/src/message/crypto.rs

@@ -110,7 +110,7 @@ impl EncryptMessage for Message<'_> {
             outer_message.extend_from_slice(
                 concat!(
                     "\"\r\n\r\n",
-                    "OpenPGP/MIME message (Automatically encrypted by Stalwart)\r\n\r\n",
+                    concat!("OpenPGP/MIME message (Automatically encrypted by ", types::brand!(), ")\r\n\r\n"),
                     "--"
                 )
                 .as_bytes(),

crates/email/src/sieve/ingest.rs

@@ -779,7 +779,7 @@ impl SieveScriptIngest for Server {
 fn write_received_header(buf: &mut Vec<u8>, hostname: &str, id: u64) {
     buf.extend_from_slice(b"Received: from localhost (localhost [127.0.0.1])\r\n\tby ");
     buf.extend_from_slice(hostname.as_bytes());
-    buf.extend_from_slice(b" (Stalwart SMTP) with LMTP id ");
+    buf.extend_from_slice(concat!(" (", types::brand!(), " SMTP) with LMTP id ").as_bytes());
     buf.extend_from_slice(format!("{id:X}").as_bytes());
     buf.extend_from_slice(b";\r\n\t");
     buf.extend_from_slice(Date::now().to_rfc822().as_bytes());