Migrate ESLint to flat config (eslint.config.mjs)

Replace legacy .eslintrc.js and .eslintignore with ESLint flat config.
- Use typescript-eslint v8 with projectService for type-aware linting
- Add eslint-plugin-jest for test file rules
- Remove unused Live Server extension recommendation
- Removed the need for eslint-plugin-import and other legacy plugins

Author: niemyjski

eslint.config.mjs

@@ -0,0 +1,44 @@
+import eslint from "@eslint/js";
+import tseslint from "typescript-eslint";
+import eslintConfigPrettier from "eslint-config-prettier";
+import jest from "eslint-plugin-jest";
+
+export default tseslint.config(
+  {
+    ignores: ["**/dist/", "**/node_modules/", "example/"]
+  },
+  eslint.configs.recommended,
+  ...tseslint.configs.recommendedTypeChecked,
+  eslintConfigPrettier,
+  {
+    languageOptions: {
+      parserOptions: {
+        projectService: {
+          allowDefaultProject: ["eslint.config.mjs"]
+        },
+        tsconfigRootDir: import.meta.dirname
+      }
+    },
+    rules: {
+      "@typescript-eslint/no-inferrable-types": "off",
+      "@typescript-eslint/no-unsafe-assignment": "off",
+      "@typescript-eslint/no-unsafe-call": "off",
+      "@typescript-eslint/no-unsafe-member-access": "off",
+      "@typescript-eslint/no-unsafe-return": "off",
+      "@typescript-eslint/no-redundant-type-constituents": "off",
+      "@typescript-eslint/no-duplicate-type-constituents": "off",
+      "@typescript-eslint/restrict-plus-operands": "off"
+    }
+  },
+  {
+    files: ["**/test/**/*.ts"],
+    ...jest.configs["flat/recommended"],
+    rules: {
+      ...jest.configs["flat/recommended"].rules,
+      "jest/valid-title": "off",
+      "jest/valid-describe-callback": "off",
+      "jest/no-export": "off",
+      "jest/no-done-callback": "warn"
+    }
+  }
+);