chore: move to eslint flat config

frontend/.eslintignore

@@ -1,13 +0,0 @@
-.DS_Store
-node_modules
-/build
-/.svelte-kit
-/package
-.env
-.env.*
-!.env.example
-
-# Ignore files for PNPM, NPM and YARN
-pnpm-lock.yaml
-package-lock.json
-yarn.lock

frontend/.eslintrc.cjs

@@ -1,15 +0,0 @@
-/** @type { import("eslint").Linter.Config } */
-module.exports = {
-	root: true,
-	extends: ['eslint:recommended', 'plugin:svelte/recommended', 'prettier'],
-	parserOptions: {
-		sourceType: 'module',
-		ecmaVersion: 2020,
-		extraFileExtensions: ['.svelte']
-	},
-	env: {
-		browser: true,
-		es2017: true,
-		node: true
-	}
-};

frontend/eslint.config.js

@@ -0,0 +1,23 @@
+import js from '@eslint/js';
+import svelte from 'eslint-plugin-svelte';
+import prettier from 'eslint-config-prettier';
+import globals from 'globals';
+
+/** @type {import('eslint').Linter.FlatConfig[]} */
+export default [
+	js.configs.recommended,
+	...svelte.configs['flat/recommended'],
+	prettier,
+	...svelte.configs['flat/prettier'],
+	{
+		languageOptions: {
+			globals: {
+				...globals.browser,
+				...globals.node
+			}
+		}
+	},
+	{
+		ignores: ['build/', '.svelte-kit/', 'dist/']
+	}
+];