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.

README.md

@@ -45,11 +45,15 @@ The report for every import is in `docs/fork/strip-reports/`. See
 ## Building
 
 ```bash
-cargo build --release -p stalwart
+cargo build --release -p inbuxa          # the binary is target/release/inbuxa
+docker build -t inbuxa .                 # or the container image
 ```
 
-The binary and package are still named `stalwart` while the packaging is
-reworked.
+Settings are read from `INBUXA_*` environment variables. An existing Stalwart
+install's `STALWART_*` variables still work, with a warning to rename them.
+New installs keep their data in `/var/lib/inbuxa` and logs in
+`/var/log/inbuxa`. Existing installs keep the paths their configuration
+already names, so none of their data moves.
 
 ## License and credits