Add AUR package (PKGBUILD) with systemd service and test script

- deploy/aur/PKGBUILD: builds from source, installs binary + man page + systemd unit
- deploy/aur/.SRCINFO: AUR metadata
- deploy/aur/test-aur.sh: tests PKGBUILD in Docker Arch container
- Supports x86_64, aarch64, armv7h architectures

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

deploy/aur/test-aur.sh

@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+# Test the PKGBUILD in a Docker Arch Linux container.
+# Usage: ./deploy/aur/test-aur.sh
+set -euo pipefail
+
+cd "$(dirname "$0")/../.."
+
+echo "=== Testing AUR PKGBUILD in Arch Linux container ==="
+
+docker run --rm -v "$(pwd):/src:ro" archlinux:latest bash -c '
+    set -euo pipefail
+
+    # Install base-devel and rust
+    pacman -Syu --noconfirm base-devel rustup git
+    rustup default stable
+
+    # Create build user (makepkg refuses to run as root)
+    useradd -m builder
+    echo "builder ALL=(ALL) NOPASSWD: ALL" >> /etc/sudoers
+
+    # Copy source and PKGBUILD
+    su builder -c "
+        mkdir -p /tmp/build && cd /tmp/build
+        cp /src/deploy/aur/PKGBUILD .
+
+        # Build the package
+        makepkg -si --noconfirm
+
+        # Verify
+        echo ''
+        echo '=== Installed ==='
+        btest --version
+        btest --help | head -5
+        echo ''
+        echo '=== Files ==='
+        pacman -Ql btest-rs
+        echo ''
+        echo '=== SUCCESS ==='
+    "
+'