license under MIT

LICENSE (MIT), installed as /usr/share/doc/terraria-server-manager/copyright
in both packages and with %license in the RPM. README gains a License
section and an up-to-date repository layout and build section.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Makefile

@@ -37,7 +37,7 @@ DEB           := build/$(NAME)_$(VERSION)_all.deb
 RPMTOP        := build/rpm
 RPM           := build/$(NAME)-$(VERSION)-1.noarch.rpm
 # What goes in the source tarball the RPM is built from
-RPM_SOURCES   := Makefile VERSION README.md CHANGELOG.md bin lib completions config docs \
+RPM_SOURCES   := Makefile VERSION LICENSE README.md CHANGELOG.md bin lib completions config docs \
                  packaging systemd tools
 
 .PHONY: all check install uninstall deb rpm clean
@@ -86,6 +86,7 @@ install:
 	install -m 644 config/tmpfiles.d/terractl.conf $(DESTDIR)$(TMPFILESDIR)/
 	install -m 644 config/polkit/terractl.rules $(DESTDIR)$(POLKITDIR)/50-terractl.rules
 	install -m 644 docs/guide.md $(DESTDIR)$(DOCDIR)/README.md
+	install -m 644 LICENSE $(DESTDIR)$(DOCDIR)/copyright
 	install -m 644 tools/windows/export-tmod-mods.ps1 $(DESTDIR)$(DATADIR)/
 	install -m 644 completions/bash/terractl $(DESTDIR)$(COMPLETIONDIR)/terractl
 	@# Never overwrite local settings