Packaging: the binary and package are inbuxa, INBUXA_* settings with STALWART_* fallback

- crates/main: package and [[bin]] renamed to inbuxa; homepage inbuxa.org;
  license AGPL-3.0-only (upstream is dual; the fork takes the AGPL).
- types::branding::env_var reads INBUXA_<name>, falling back to
  STALWART_<name> with a warning, for all nine server settings.
  STALWART_APP_ and STALWART_SPAM_* storage keys are unchanged.
- New-install default paths /var/lib/inbuxa and /var/log/inbuxa.
- Dockerfiles, systemd unit, launchd plist and AppArmor profile renamed.
- Upstream's .github moved to .github-upstream so none of it runs.
- install.sh stubbed: upstream's would install Stalwart.
- Two missed brand strings: the SMTP Received header and the utils user agent.

crates/common/src/config/telemetry.rs

@@ -503,7 +503,7 @@ impl Tracers {
             }
         } else {
             // Add default tracer if none were found
-            let level = std::env::var("STALWART_RECOVERY_MODE_LOG_LEVEL")
+            let level = types::branding::env_var("RECOVERY_MODE_LOG_LEVEL")
                 .ok()
                 .and_then(|level| Level::from_str(&level).ok())
                 .unwrap_or(Level::Info);