refactor: organize tests and extract formatting utilities

- Move test files to lib/__tests__/ directory
- Extract formatting utilities (formatVersion, formatFileSize, formatDateTime)
  from fs-utils.ts to new utils.ts module
- Add Jest test configuration and test scripts
- Update component imports to use new utils module
- Add CLAUDE.md documentation for project structure

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

jest.config.js

@@ -0,0 +1,28 @@
+const nextJest = require('next/jest')
+
+const createJestConfig = nextJest({
+  // Provide the path to your Next.js app to load next.config.js and .env files in your test environment
+  dir: './',
+})
+
+// Add any custom config to be passed to Jest
+const customJestConfig = {
+  setupFilesAfterEnv: ['<rootDir>/jest.setup.js'],
+  testEnvironment: 'jest-environment-jsdom',
+  moduleNameMapper: {
+    '^@/(.*)$': '<rootDir>/$1',
+  },
+  testMatch: [
+    '**/__tests__/**/*.test.{ts,tsx,js,jsx}',
+    '**/*.test.{ts,tsx,js,jsx}',
+  ],
+  collectCoverageFrom: [
+    'lib/**/*.{ts,tsx}',
+    'app/**/*.{ts,tsx}',
+    '!app/**/*.stories.{ts,tsx}',
+    '!app/layout.{ts,tsx}',
+  ],
+}
+
+// createJestConfig is exported this way to ensure that next/jest can load the Next.js config which is async
+module.exports = createJestConfig(customJestConfig)