Add reproducible build system, native Unraid plugin, and WebUI

- versions.env pins podman, conmon, crun, netavark, aardvark-dns, passt,
  and fuse-overlayfs to verified upstream source checksums; SlackBuild
  recipes, scripts/build-packages.sh, checksums.sh, release.sh, and
  update-versions.sh implement the reproducible pipeline; GitHub Actions
  workflows build in a Slackware container and publish releases without
  committing any binaries.

- plugin/podman.plg installs/updates/removes all eight packages (the
  seven components plus the plugin's own unraid-podman scaffolding
  package) via upgradepkg, using the official Unraid array-event hook
  mechanism (event/disks_mounted, event/stopping) instead of editing
  /boot/config/go. rc.podman and the sbin/ helper scripts implement
  storage creation, config seeding/sync, preflight checks, autostart
  with per-container Safe-Mode, and package verify/update/rollback.

- webui/plugins/podman implements the Dashboard, Containers, Pods,
  Images, Volumes, Networks, Logs, Terminal, Compose, and Settings
  panels against the approved mockup (webui/mockups/prototype.html),
  talking to podman system service exclusively via PodmanClient.php
  (libpod REST API over the Unix socket), with two documented
  exceptions: Terminal's one-shot exec model and Compose's use of the
  podman compose CLI, since libpod has no REST equivalent for either.

- docs/ARCHITECTURE.md and docs/ROADMAP.md record the design decisions
  and honest current status (syntax-checked, unit- and
  integration-tested against fake sockets/servers; not yet run against
  a real Unraid/Podman/Slackware system).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

packages/netavark/README.md

@@ -0,0 +1,15 @@
+# packages/netavark
+
+Slackware package build recipe for **netavark**.
+
+- Upstream: https://github.com/containers/netavark
+- Pinned version: TODO
+- Patches: see `patches/` (currently none)
+- Build entry point: `netavark.SlackBuild` (placeholder, not yet implemented)
+
+## Notes
+
+TODO: document any Unraid/Slackware-specific build considerations (static
+linking, cgroup v2 assumptions, kernel feature requirements) once the build
+script is implemented. See
+[docs/ARCHITECTURE.md, section 5.2 (Build-Strategie)](../../docs/ARCHITECTURE.md#52-build-strategie).

packages/netavark/netavark.SlackBuild

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+#!/bin/bash
+# =============================================================================
+# packages/netavark/netavark.SlackBuild
+#
+# Builds the netavark .txz package from upstream source (Rust). netavark is
+# this project's container networking backend (see docs/ARCHITECTURE.md
+# section 8) — it is installed as a libexec helper binary, not a $PATH tool,
+# matching upstream's own layout so podman finds it via
+# `netavark_binary_dir` in containers.conf.
+#
+# Requires (in the build environment): rustc, cargo (a recent stable
+# toolchain — check upstream's Cargo.toml `rust-version` for the current
+# minimum).
+# =============================================================================
+
+set -eu
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+# shellcheck source=/dev/null
+. "$REPO_ROOT/scripts/lib/slackbuild-common.sh"
+# shellcheck source=/dev/null
+. "$REPO_ROOT/versions.env"
+
+VERSION="$NETAVARK_VERSION"
+ARCH="$PKG_ARCH"
+BUILD="$PKG_BUILD"
+TAG="$PKG_TAG"
+
+sb_init "netavark"
+
+tarball=$(sb_fetch_and_verify "$NETAVARK_SRC_URL" "$NETAVARK_SRC_SHA256" "netavark-$VERSION.tar.gz")
+srcdir=$(sb_extract "$tarball")
+
+for patch in "$CWD"/patches/*.patch; do
+  [ -e "$patch" ] || continue
+  echo "==> [netavark] applying $(basename "$patch")"
+  patch -d "$srcdir" -p1 < "$patch"
+done
+
+cd "$srcdir"
+
+echo "==> [netavark] cargo build --release"
+cargo build --release --locked
+
+echo "==> [netavark] install into \$PKG"
+install -D -m 0755 target/release/netavark "$PKG/usr/libexec/podman/netavark"
+
+sb_install_docs "$srcdir/LICENSE" "$srcdir/README.md"
+sb_make_package "$VERSION" "$ARCH" "$BUILD" "$TAG"

packages/netavark/slack-desc

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+# HOW TO EDIT THIS FILE:
+# The "handy ruler" below makes it easier to edit a package description.
+# Line up the first '|' above the ':' following the base package name, and
+# the '|' on the right side marks the last column you can put a character in.
+# You must make exactly 11 lines for the formatting to be correct. It's also
+# customary to leave one space after the ':' except on otherwise blank lines.
+
+        |-----handy-ruler------------------------------------------------|
+netavark: netavark (TODO: one-line summary)
+netavark:
+netavark: TODO: two-to-three sentence description of netavark, its role in the
+netavark: unraid-podman plugin, and a link to the upstream project.
+netavark:
+netavark: Homepage: https://github.com/containers/netavark
+netavark:
+netavark:
+netavark:
+netavark:
+netavark: