Fix the staged install link used by DESTDIR

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

deploy/install.sh

@@ -51,7 +51,9 @@ mkdir -p "$LIB"
 install -m 0755 "$HERE/$NAME" "$LIB/$NAME.new"
 mv -f "$LIB/$NAME.new" "$LIB/$NAME" # atomic, so upgrading a running service is safe
 rm -f "$BIN"
-ln -s "/usr/local/lib/$NAME/$NAME" "$BIN"
+LINK=/usr/local/lib/$NAME/$NAME
+[ -z "${DESTDIR:-}" ] || LINK=$LIB/$NAME # staging: point inside the staging folder
+ln -s "$LINK" "$BIN"
 install -m 0644 "$HERE/$NAME.service" "$UNIT"
 if [ ! -f "$ENVFILE" ]; then
 	install -m 0600 "$HERE/.env.example" "$ENVFILE"