ci(rpm): publish punktfunk-host RPM to the Gitea registry (Bazzite)

Mirrors the apt pipeline for Fedora Atomic / Bazzite. New `rpm` workflow builds
the host RPM in a Fedora 43 builder image (ci/fedora-rpm.Dockerfile — matches
Bazzite's libavcodec.so.61, with a self-contained 16-symbol libcuda link stub so
no NVIDIA packages are needed in CI) and uploads to Gitea's public RPM registry
(group "bazzite") on every main push (rolling 0.0.1-0.ciN.<sha>) and v* tag
(clean X.Y.Z-1). Bazzite hosts then track it with `rpm-ostree upgrade`.

- packaging/rpm/build-rpm.sh: git-archive tarball + rpmbuild (--nodeps, since the
  toolchain is rustup + dnf, not RPMs); copies to dist/, asserts no cuda/nvidia leak.
- punktfunk.spec: overridable pf_version/pf_release for CI snapshots; exclude
  libcuda.so from auto-Requires (NVENC/EGL come from the driver, out of band) —
  same NVIDIA filter as the .deb; fix a bogus changelog weekday.
- docker.yml builds+pushes the new fedora-rpm image; packaging README + rpm/README
  document the rpm-ostree install/update path (recommended option).

Builder image seeded to the registry so rpm.yml's first run finds it. RPM build +
clean-Requires verified locally in the image (libavcodec.so.61 / libavutil.so.59,
no cuda).

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

packaging/README.md

@@ -33,7 +33,20 @@ On **Bazzite** the only genuinely new runtime bits are `ffmpeg-libs` (RPM Fusion
 `libei` — the rest of the stack is already there. The default backend is **gamescope**
 (`packaging/bazzite/host.env`), which the host spawns headless per session — no desktop login.
 
-## Option A — COPR (per-host, `rpm-ostree install`)
+## Option A — Gitea RPM registry (recommended; per-host, `rpm-ostree`)
+
+The host's RPM is published to **unom's self-hosted Gitea RPM registry** (CI builds it on every
+push), mirroring the [Debian/apt](debian/README.md) setup. Add one repo file, install, and track
+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
+rpm-ostree install punktfunk && systemctl reboot
+# updates:  rpm-ostree upgrade && systemctl reboot
+```
+
+## Option B — COPR (per-host, `rpm-ostree install`)
 
 1. Create a COPR project, enable **build-from-SCM** pointing at this repo, spec path
    `packaging/rpm/punktfunk.spec` (see `copr/README.md`). Under *External Repositories* add