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/common/src/config/mailstore/scripts.rs

@@ -90,7 +90,7 @@ impl Scripting {
             .with_protected_headers(untrusted.protected_headers)
             .with_vacation_default_subject(untrusted.default_subject)
             .with_vacation_subject_prefix(untrusted.default_subject_prefix)
-            .with_env_variable("name", "Stalwart Server")
+            .with_env_variable("name", types::brand_server!())
             .with_env_variable("version", VERSION_PUBLIC)
             .with_env_variable("location", "MS")
             .with_env_variable("phase", "during");