build: update to node 22 and pnpm (#3616)

This commit brings the project to support node 22 which became LTS and
fixes broken builds with typescript 5.7+ until vue-tsc is updated and
replaces npm with pnpm.

- Update tsconfig for node 22
- Pin typescript to 5.6.x to not break vue-tsc
- Replace npm with pnpm (corepack recommended)
- Update Makefile and main workflow for pnpm
- Migrate to eslint 9 flat config
- Fix broken imports
- Exclude non-TS vue files for vue-tsc

frontend/eslint.config.js

@@ -0,0 +1,39 @@
+import pluginVue from "eslint-plugin-vue";
+import vueTsEslintConfig from "@vue/eslint-config-typescript";
+import prettierConfig from "@vue/eslint-config-prettier";
+
+export default [
+  {
+    name: "app/files-to-lint",
+    files: ["**/*.{ts,mts,tsx,vue}"],
+  },
+
+  {
+    name: "app/files-to-ignore",
+    ignores: ["**/dist/**", "**/dist-ssr/**", "**/coverage/**"],
+  },
+
+  ...pluginVue.configs["flat/essential"],
+  ...vueTsEslintConfig(),
+  prettierConfig,
+
+  {
+    rules: {
+      "no-var": "warn",
+      "prefer-const": "warn",
+      // Note: you must disable the base rule as it can report incorrect errors
+      "no-unused-expressions": "off",
+      "@typescript-eslint/no-unused-expressions": "warn",
+      "@typescript-eslint/no-explicit-any": "warn",
+      "@typescript-eslint/ban-ts-comment": "warn",
+      "vue/block-lang": "warn",
+      "vue/multi-word-component-names": "off",
+      "vue/no-mutating-props": [
+        "error",
+        {
+          shallowOnly: true,
+        },
+      ],
+    },
+  },
+];