feat(doorman): badge listener + decoder TDD + deploy scaffolding [#355]

Modern successor of the 2018 Perl doorman (snapshot in legacy/):
bash+coreutils HID decoder, HA webhook dispatch, systemd unit.
Offline decoder suite green (9 tests); shellcheck zero-warning.

Umbrella #345. Work item: https://projects.knownelement.com/issues/355

scripts/test.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+#
+# scripts/test.sh — project test runner (framework entry point).
+#
+# LOCAL GATE: offline decoder unit suite; no hardware required (#355
+# scope: "test logic on the laptop").
+#
+set -uo pipefail
+cd "$(dirname "${BASH_SOURCE[0]}")/.." || exit 1
+
+status=0
+bash tests/run-tests.sh || status=1
+
+exit "$status"