Migrate tests from Jest to Vitest, updating setup and test files accordingly.

- Replace Jest imports and mocks with Vitest equivalents in setup and unit tests.
- Adjust test cases to use async imports and reset modules with Vitest.
- Add Vitest configuration file for test environment setup and coverage reporting.

vitest.config.mts

@@ -0,0 +1,23 @@
+import { defineConfig } from 'vitest/config'
+import react from '@vitejs/plugin-react'
+import tsconfigPaths from 'vite-tsconfig-paths'
+
+export default defineConfig({
+  plugins: [tsconfigPaths(), react()],
+  test: {
+    environment: 'node',
+    globals: true,
+    setupFiles: ['./tests/setup.ts'],
+    include: ['tests/**/*.{test,spec}.{js,mjs,cjs,ts,mts,cts,jsx,tsx}'],
+    env: {
+      NODE_ENV: 'test',
+    },
+    coverage: {
+      provider: 'v8',
+      reporter: ['text', 'lcov', 'html'],
+      include: ['lib/**/*.ts'],
+      exclude: ['lib/**/*.d.ts', 'lib/**/*.test.ts'],
+    },
+    testTimeout: 10000,
+  },
+})