ci: add lint workflow, shellcheck fixes, and CI failure hookshot alert

- .gitea/workflows/lint.yml: new workflow running shellcheck on .sh files
  and eslint on hookshot/ JS transform scripts
- hookshot/.eslintrc.json: declare data/result as hookshot globals
- hookshot/ci-alert.js: new Matrix hookshot transform for CI failure alerts
- hookshot/deploy.sh: fix SC2155 (split local/assign), SC2034 (remove unused var)
- systemd/livekit-clear-port.sh: fix SC2148 (invalid shebang escape)
- cinny/dev-update.sh: fix SC2115 (use ${WEB_ROOT:?} to guard rm -rf)
- deploy/lxc151-hookshot.sh: add shellcheck source=/dev/null for sourced file
- .gitignore: ignore node_modules/
- package.json + package-lock.json: eslint@8 dev dependency

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

hookshot/.eslintrc.json

@@ -0,0 +1,14 @@
+{
+    "env": { "es2021": true },
+    "parserOptions": { "ecmaVersion": 2021 },
+    "globals": {
+        "data": "readonly",
+        "result": "writable"
+    },
+    "rules": {
+        "no-unused-vars": "warn",
+        "no-undef": "error",
+        "semi": ["error", "always"],
+        "eqeqeq": "warn"
+    }
+}