Add jellyfin-ha container build

Build-orchestration for the jellyfin-ha Jellyfin fork: pins an upstream
commit (UPSTREAM_REF), publishes the .NET 10 server, and builds/pushes the
runtime image to git.unkin.net/unkin/jellyfin-ha on v* tags.

- UPSTREAM_REF pinned to d4f9c12
- Dockerfile.runtime (vendored runtime-only image + jellyfin-web 10.11.6)
- .woodpecker/{build,docker}.yaml (publish + docker-buildx, k8s resources)
- Makefile (publish/build + patch/minor/major release tagging)

Dockerfile.runtime

@@ -0,0 +1,57 @@
+# syntax=docker/dockerfile:1
+# Runtime-only image for the jellyfin-ha fork.
+#
+# The .NET publish step runs on the CI host (see .woodpecker/*.yaml) and drops
+# its output into ./publish-output, which is COPYed in below. This file is a
+# vendored copy of upstream's Dockerfile.runtime so we control the pinned
+# jellyfin-web version and base image; bump alongside UPSTREAM_REF.
+
+# ── Web client stage ──────────────────────────────────────────────────────────
+# Install jellyfin-web via the official Jellyfin apt repo (prebuilt, no npm).
+# Web assets land at /usr/share/jellyfin/web/.
+FROM --platform=linux/amd64 debian:bookworm-slim AS webclient
+
+RUN apt-get update \
+ && apt-get install -y --no-install-recommends curl gnupg ca-certificates \
+ && curl -fsSL https://repo.jellyfin.org/jellyfin_team.gpg.key \
+    | gpg --dearmor -o /usr/share/keyrings/jellyfin.gpg \
+ && echo "deb [arch=amd64 signed-by=/usr/share/keyrings/jellyfin.gpg] https://repo.jellyfin.org/debian bookworm main" \
+    > /etc/apt/sources.list.d/jellyfin.list \
+ && apt-get update \
+ && apt-get install -y --no-install-recommends "jellyfin-web=10.11.6+deb12" \
+ && rm -rf /var/lib/apt/lists/*
+
+# ── Runtime stage ─────────────────────────────────────────────────────────────
+FROM --platform=linux/amd64 mcr.microsoft.com/dotnet/aspnet:10.0
+
+# FFmpeg and the native deps required by SkiaSharp and fontconfig.
+RUN apt-get update \
+ && apt-get install -y --no-install-recommends \
+      ffmpeg \
+      fontconfig \
+      libfontconfig1 \
+      libfreetype6 \
+ && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /jellyfin
+
+# Pre-built publish output produced by `dotnet publish` on the CI host.
+COPY publish-output/ .
+# jellyfin-web client assets from the webclient stage.
+COPY --from=webclient /usr/share/jellyfin/web ./jellyfin-web/
+
+# Jellyfin default ports
+EXPOSE 8096
+EXPOSE 8920
+
+# Data / config volumes
+VOLUME ["/config", "/cache", "/media"]
+
+ENV JELLYFIN_DATA_DIR=/config \
+    JELLYFIN_CACHE_DIR=/cache \
+    JELLYFIN_LOG_DIR=/config/log
+
+ENTRYPOINT ["./jellyfin", \
+            "--datadir", "/config", \
+            "--cachedir", "/cache", \
+            "--webdir", "/jellyfin/jellyfin-web"]