track cross-build cargo config + souveraine user unit

.cargo/config.toml + aarch64-pkg-config wrapper are load-bearing for the
cross build (CI artifact job + local build-cross.sh both depend on them);
were gitignored before. souveraine.service is the systemd user unit the
packaging/deploy scripts template.

.cargo/aarch64-pkg-config

@@ -0,0 +1,10 @@
+#!/bin/bash
+# ponytail: cross pkg-config wrapper for aarch64-unknown-linux-gnu.
+# cargo's [env] block doesn't reliably reach build-script pkg-config probes,
+# so alsa-sys's built-in cross guard trips. This wrapper sets the vars itself
+# and is referenced via PKG_CONFIG in .cargo/config.toml — every pkg-config
+# probe in the tree (alsa-sys today, any future -sys crate) goes through it.
+export PKG_CONFIG_ALLOW_CROSS=1
+export PKG_CONFIG_LIBDIR=/usr/aarch64-linux-gnu/lib/pkgconfig
+export PKG_CONFIG_SYSROOT_DIR=/usr/aarch64-linux-gnu
+exec /usr/bin/pkg-config "$@"

.cargo/config.toml

@@ -0,0 +1,10 @@
+# ponytail: cross-build target for the Pixel 3 / any aarch64 Arch box.
+# Sysroot (/usr/aarch64-linux-gnu, from the aarch64-linux-gnu-gcc/glibc Arch
+# packages) holds glibc 2.43 + the cross alsa-lib we built in. Linker is the
+# cross gcc.
+#
+# The PKG_CONFIG_* vars alsa-sys needs are NOT set here — cargo's [env] block
+# doesn't reliably reach build-script pkg-config probes. scripts/build-cross.sh
+# exports them on the cargo invocation so they inherit to every build script.
+[target.aarch64-unknown-linux-gnu]
+linker = "aarch64-linux-gnu-gcc"

packaging/souveraine.service

@@ -0,0 +1,14 @@
+# Souveraine server — systemd user unit.
+# Install: cp to ~/.config/systemd/user/ && systemctl --user enable --now souveraine
+# The quickshell surface starts this on demand when autostart is enabled.
+[Unit]
+Description=Souveraine server
+After=network.target
+
+[Service]
+ExecStart=%h/.local/bin/souveraine server
+Restart=on-failure
+RestartSec=5
+
+[Install]
+WantedBy=default.target