chore(configs): migrate oxlint→eslint presets, refactor tsconfig

- Replace @robonen/oxlint with @robonen/eslint (composable ESLint flat-config
  presets: base, typescript, vue, vitest, imports, node, stylistic).
- Plugins bundled as deps: typescript-eslint, eslint-plugin-vue,
  @vitest/eslint-plugin, eslint-plugin-import-x, eslint-plugin-n,
  eslint-plugin-unicorn, @stylistic/eslint-plugin.
- @robonen/tsconfig: add base/dom/node/vue configs for composite project refs.

configs/eslint/vitest.config.ts

@@ -0,0 +1,7 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    environment: 'node',
+  },
+});