chore(linting): update ESLint to latest version (#6430)

# Motivation

We want to update ESLint to its latest version, as it is no longer
supported. This follows up on #6391, and it is important because
ESLint@8 is outdated.

![Screenshot 2025-02-15 at 11 30
43](https://github.com/user-attachments/assets/c6228b1b-6f13-4980-8348-82341828b486)

To minimize the necessary changes due to the differences in how some
rules apply now compared to before, I've overwritten certain rules. This
will be addressed in a follow-up.

# Changes

- Upgrades ESLint and relevant packages to the latest version.  
- Installs new required packages.  
- Removes packages that are no longer needed.  

# Tests

- Linting should pass as it did previously.

# Todos

- [ ] Add entry to changelog (if necessary).
Not necessary

frontend/eslint.config.mjs

@@ -0,0 +1,84 @@
+import jsLint from "@eslint/js";
+import prettierPlugin from "eslint-config-prettier";
+import sveltePlugin from "eslint-plugin-svelte";
+import globals from "globals";
+import svelteParser from "svelte-eslint-parser";
+import tsLint from "typescript-eslint";
+import svelteConfig from "./svelte.config.js";
+
+export default [
+  jsLint.configs.recommended,
+  ...tsLint.configs.recommended,
+  {
+    name: "globals",
+    languageOptions: {
+      globals: {
+        ...globals.browser,
+        ...globals.node,
+        NodeJS: true,
+      },
+      parser: tsLint.parser,
+      ecmaVersion: 2020,
+      sourceType: "module",
+      parserOptions: {
+        extraFileExtensions: [".svelte"],
+      },
+    },
+    rules: {
+      "@typescript-eslint/no-unused-vars": [
+        "warn",
+        {
+          argsIgnorePattern: "^_",
+          varsIgnorePattern: "^_",
+          caughtErrorsIgnorePattern: "^_",
+        },
+      ],
+      "no-underscore-dangle": "off",
+      // TODO: Fix after migration
+      "no-constant-binary-expression": "off",
+      "@typescript-eslint/no-empty-object-type": "off",
+      "@typescript-eslint/no-unused-expressions": "off",
+    },
+  },
+  ...sveltePlugin.configs["flat/recommended"],
+  {
+    name: "svelte",
+    files: ["**/*.svelte"],
+    languageOptions: {
+      parser: svelteParser,
+      parserOptions: {
+        parser: tsLint.parser,
+        svelteConfig,
+      },
+    },
+  },
+  prettierPlugin,
+  {
+    name: "ignores",
+    ignores: [
+      // ignorePatterns
+      "src/lib/canisters/**/*",
+      // .eslintignore
+      "**/.DS_Store",
+      "build",
+      ".svelte-kit",
+      "package",
+      "playwright*",
+      "**/.env",
+      "**/.env.*",
+      "!**/.env.example",
+      // Ignore files for PNPM, NPM and YARN
+      "**/pnpm-lock.yaml",
+      "**/package-lock.json",
+      "**/yarn.lock",
+
+      "static",
+      "public",
+      "scripts",
+
+      "src/lib/canisters/nns-dapp/**/*",
+
+      "**/coverage",
+    ],
+  },
+];