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.

resources/apparmor.d/inbuxa

@@ -1,6 +1,6 @@
 #include <tunables/global>
 
-profile stalwart flags=(attach_disconnected) {
+profile inbuxa flags=(attach_disconnected) {
   #include <abstractions/base>
   #include <abstractions/nameservice>
   #include <abstractions/openssl>
@@ -17,8 +17,8 @@ profile stalwart flags=(attach_disconnected) {
   owner /proc/*/net/if_inet6 r,
   owner /proc/*/net/ipv6_route r,
 
-  # Full write access to /opt/stalwart
-  /opt/stalwart/** rwk,
+  # Full write access to /opt/inbuxa
+  /opt/inbuxa/** rwk,
 
   # Allow creating directories under /tmp
   /tmp/ r,
@@ -51,9 +51,9 @@ profile stalwart flags=(attach_disconnected) {
   network inet6 dgram bind port 7911,
 
   # Basic system access
-  /usr/bin/stalwart rix,
-  /etc/stalwart/** r,
-  /var/log/stalwart/** w,
+  /usr/bin/inbuxa rix,
+  /etc/inbuxa/** r,
+  /var/log/inbuxa/** w,
 
   # Additional permissions might be needed depending on specific requirements
 }