feat: Linux packaging, SDK v0.7.1, fix rawmode conflict

- go.mod: SDK pseudo-version -> v0.7.1 (remote tag), go.sum updated
- cmd/waiter/rawmode_linux.go: remove (conflicts with raw_unix.go)
- cmd/gui/package.json: add rpm/AppImage Linux targets
- package/package-linux.sh: cross-distro packaging script (deb/tar.gz/rpm)
- package/linux/: DEBIAN control files, postinst/prerm, RPM spec

package/linux/deb/prerm

@@ -0,0 +1,19 @@
+#!/bin/sh
+set -e
+
+SERVICE_NAME="homeagent"
+
+case "$1" in
+  remove|deconfigure)
+    if command -v systemctl >/dev/null 2>&1; then
+      systemctl stop "$SERVICE_NAME" 2>/dev/null || true
+      systemctl disable "$SERVICE_NAME" 2>/dev/null || true
+    fi
+    ;;
+  upgrade)
+    ;;
+  *)
+    ;;
+esac
+
+exit 0