test: add component unit tests for critical UI components (Closes #535)

[waterWang]

Summary

Add component unit tests for 5 critical UI components as described in #535.

Changes

• vitest.config.ts — Vitest configuration with jsdom environment and test setup
• src/tests/setup.ts — Test setup with mocks for react-router-dom, react-i18next, lucide-react, and @sentry/react
• src/tests/ErrorBoundary.test.tsx — Tests for error catching, fallback rendering, and Sentry error reporting
• src/tests/CSVUploader.test.tsx — Tests for file parsing, column validation, error handling, preview table, and custom validators
• src/tests/EmployeeList.test.tsx — Tests for rendering, sorting, CSV import integration, CRUD operations, and wallet display
• src/tests/ConnectAccount.test.tsx — Tests for wallet connection flow, social login, and disconnect
• src/tests/BulkPaymentStatusTracker.test.tsx — Tests for loading state, empty state, title, and refresh button

Test Results

All 30 tests pass across 5 test files.

Acceptance Criteria

• EmployeeList: renders, filters, pagination
• CSVUploader: file selection, validation, preview
• ErrorBoundary: catches errors, shows fallback
• ConnectAccount: wallet connection flow