feat(v5.2.0): finalize Infrastructure & Polish (tests isolation, xdist, lint, CI)

tests/conftest.py: mutate the settings singleton (instead of rebinding) so DB + backup dir are isolated per test -> pytest-xdist safe.
Real backup tests (snapshot/prune/admin API) and OAuth mock tests (Gitea/GitHub/link) replace the previous skips.
init_db() now also creates webhook_subscriptions (full schema without the FastAPI lifespan).
ruff check is clean; .eslintrc.json migrated to eslint.config.mjs (flat config).
CI: lint job (ruff + eslint), parallel tests (-n auto), run on every branch push.
VERSION 5.11.1.

eslint.config.mjs

@@ -0,0 +1,63 @@
+// FlowDeck — ESLint flat config (v5.2.0).
+// ESLint v9+ requires the flat config format; the legacy `.eslintrc.json`
+// is no longer read. Run with: `npx eslint static/js`.
+//
+// Self-contained on purpose: no dependency on the `globals` npm package so the
+// config works with a globally-installed ESLint (no node_modules required).
+
+const browserGlobals = {
+  // Browser / DOM
+  window: "readonly", document: "readonly", navigator: "readonly",
+  location: "readonly", history: "readonly", screen: "readonly",
+  localStorage: "readonly", sessionStorage: "readonly", console: "readonly",
+  alert: "readonly", confirm: "readonly", prompt: "readonly", fetch: "readonly",
+  setTimeout: "readonly", clearTimeout: "readonly", setInterval: "readonly",
+  clearInterval: "readonly", requestAnimationFrame: "readonly",
+  cancelAnimationFrame: "readonly", requestIdleCallback: "readonly",
+  cancelIdleCallback: "readonly", queueMicrotask: "readonly",
+  XMLHttpRequest: "readonly", FormData: "readonly", Blob: "readonly",
+  File: "readonly", FileReader: "readonly", URL: "readonly",
+  URLSearchParams: "readonly", Image: "readonly", Event: "readonly",
+  CustomEvent: "readonly", EventSource: "readonly", WebSocket: "readonly",
+  DOMParser: "readonly", Node: "readonly", NodeList: "readonly",
+  Element: "readonly", HTMLElement: "readonly", getComputedStyle: "readonly",
+  matchMedia: "readonly", IntersectionObserver: "readonly",
+  MutationObserver: "readonly", ResizeObserver: "readonly",
+  performance: "readonly", crypto: "readonly", btoa: "readonly",
+  atob: "readonly", structuredClone: "readonly",
+  // ECMAScript built-ins
+  JSON: "readonly", Math: "readonly", Date: "readonly", Promise: "readonly",
+  Object: "readonly", Array: "readonly", String: "readonly", Number: "readonly",
+  Boolean: "readonly", Symbol: "readonly", Map: "readonly", Set: "readonly",
+  WeakMap: "readonly", WeakSet: "readonly", Error: "readonly",
+  TypeError: "readonly", RangeError: "readonly", RegExp: "readonly",
+  Proxy: "readonly", Reflect: "readonly", Intl: "readonly",
+  parseInt: "readonly", parseFloat: "readonly", isNaN: "readonly",
+  isFinite: "readonly", encodeURIComponent: "readonly",
+  decodeURIComponent: "readonly", encodeURI: "readonly", decodeURI: "readonly",
+  globalThis: "readonly", Infinity: "readonly", NaN: "readonly",
+  // FlowDeck front-end libraries
+  Alpine: "readonly", htmx: "readonly", Sortable: "readonly",
+  // Globals exposed on window by app.js
+  openModal: "readonly", closeModal: "readonly",
+};
+
+export default [
+  {
+    ignores: ["static/js/*.min.js", "static/js/vendor/**"],
+  },
+  {
+    files: ["static/js/**/*.js"],
+    languageOptions: {
+      ecmaVersion: 2022,
+      sourceType: "script",
+      globals: browserGlobals,
+    },
+    rules: {
+      "no-unused-vars": ["warn", { args: "none" }],
+      "no-undef": "warn",
+      "no-extra-semi": "warn",
+      "no-empty": "warn",
+    },
+  },
+];