docs(rpm): use repo_gpgcheck for the unsigned Gitea RPMs

Gitea GPG-signs the repo metadata but not the individual packages, while its
auto-served bazzite.repo sets gpgcheck=1 — so `rpm-ostree install` fails with
"could not be verified" on our unsigned RPMs. Document writing the repo
explicitly with gpgcheck=0 + repo_gpgcheck=1 (verify the signed metadata, which
carries each package checksum) instead of curling the served .repo. Note the
TLS-only fallback and that per-package signing is future hardening.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packaging/README.md

@@ -40,8 +40,16 @@ push), mirroring the [Debian/apt](debian/README.md) setup. Add one repo file, in
 updates with `rpm-ostree upgrade` — no COPR account needed. Full guide: [`rpm/README.md`](rpm/README.md).
 
 ```sh
-curl -fsSL https://git.unom.io/api/packages/unom/rpm/bazzite.repo \
-  | sudo tee /etc/yum.repos.d/punktfunk.repo
+# unsigned pkgs + Gitea-signed metadata → repo_gpgcheck=1, gpgcheck=0 (see rpm/README.md)
+sudo tee /etc/yum.repos.d/punktfunk.repo >/dev/null <<'REPO'
+[gitea-unom-bazzite]
+name=punktfunk (unom, Bazzite)
+baseurl=https://git.unom.io/api/packages/unom/rpm/bazzite
+enabled=1
+gpgcheck=0
+repo_gpgcheck=1
+gpgkey=https://git.unom.io/api/packages/unom/rpm/repository.key
+REPO
 rpm-ostree install punktfunk && systemctl reboot
 # updates:  rpm-ostree upgrade && systemctl reboot
 ```

packaging/rpm/README.md

@@ -15,15 +15,29 @@ paths — same spec (`punktfunk.spec`) — just self-hosted in Gitea instead of
 ## Install on a Bazzite host (one-time)
 
 ```sh
-# Trust + add the repo (rpm-ostree reads /etc/yum.repos.d). Public registry, no auth.
-curl -fsSL https://git.unom.io/api/packages/unom/rpm/bazzite.repo \
-  | sudo tee /etc/yum.repos.d/punktfunk.repo
+# Add the repo. Our RPMs are unsigned, but Gitea GPG-signs the repo METADATA — so verify that
+# (repo_gpgcheck=1) and skip the per-package signature check (gpgcheck=0). The signed metadata
+# carries each package's SHA256, so authenticity still holds. (Don't just curl Gitea's served
+# bazzite.repo — it sets gpgcheck=1, which fails on unsigned packages.)
+sudo tee /etc/yum.repos.d/punktfunk.repo >/dev/null <<'REPO'
+[gitea-unom-bazzite]
+name=punktfunk (unom, Bazzite)
+baseurl=https://git.unom.io/api/packages/unom/rpm/bazzite
+enabled=1
+gpgcheck=0
+repo_gpgcheck=1
+gpgkey=https://git.unom.io/api/packages/unom/rpm/repository.key
+REPO
 
 # Layer the package, then reboot into the new deployment.
 rpm-ostree install punktfunk
 systemctl reboot
 ```
 
+> If `rpm-ostree` can't complete the metadata GPG check non-interactively, set `repo_gpgcheck=0`
+> (TLS-only trust to the self-hosted registry). Proper per-package signing (`gpgcheck=1`) would
+> need a CI signing key + `rpm --addsign` — future hardening, not wired up.
+
 After reboot, as the desktop user:
 
 ```sh