add rpm packaging; dnf and firewalld support

- packaging/rpm/terraria-server-manager.spec.in: installs via make
  install, plain scriptlets (no Fedora-only macros) mirroring the deb
  maintainer scripts; removal stops servers, disables boot/backups/
  daemon and removes only terractl's own drop-ins.
- make rpm (rpmbuild --nodeps, works on Debian/Ubuntu); make check
  parses the spec when rpmspec is installed.
- Release workflow builds deb and rpm, attaches both, publishes the rpm
  to Gitea's RPM registry. Job renamed to 'packages'.
- pkg_install: install hints use dnf or apt with the right package
  names (doctor, fetch, python3/openssl checks).
- firewalld: new prints the firewall-cmd command for its port; doctor
  lists instance and daemon ports firewalld doesn't allow.
- Docs, README, AGENTS.md and changelog; VERSION 0.0.13.

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

README.md

@@ -28,7 +28,7 @@ sudo terractl attach calamity
 
 ## Requirements
 
-- Debian 12+ or Ubuntu 22.04+ (other systemd-based distributions should work with `make install`)
+- Debian 12+ or Ubuntu 22.04+ (`.deb`), or Fedora, RHEL 9+ and compatible (`.rpm`); other systemd-based distributions should work with `make install`
 - `unzip`, `systemd`; for tModLoader, also `curl` and ICU (`libicu`)
 - `python3` and `openssl`, for managing other hosts
 
@@ -46,10 +46,19 @@ sudo apt update
 sudo apt install terraria-server-manager
 ```
 
-Or download the `.deb` from the releases page, then:
+On Fedora, RHEL and compatible, from the RPM repository:
 
 ```bash
-sudo apt install ./terraria-server-manager_<version>_all.deb
+sudo curl -fsSL https://gitea.adbraun.lol/api/packages/adam/rpm.repo \
+  -o /etc/yum.repos.d/terraria-server-manager.repo
+sudo dnf install terraria-server-manager
+```
+
+Or download the `.deb` or `.rpm` from the releases page, then:
+
+```bash
+sudo apt install ./terraria-server-manager_<version>_all.deb       # Debian, Ubuntu
+sudo dnf install ./terraria-server-manager-<version>-1.noarch.rpm  # Fedora, RHEL
 ```
 
 Or install from source, without a package: