Phase 2 WIP: MSW setup + useBoards tests complete

Progress:
- Set up MSW (Mock Service Worker) for API mocking
- Created comprehensive MSW handlers for all API endpoints
- Configured environment variables for test API URLs
- Wrote 14 passing tests for useBoards hook

Tests Implemented (useBoards):
- GetBoards query (loading, success, error states)
- GetBoard query (single board fetch, multiple IDs)
- createBoard mutation (success, error, org_id validation)
- updateBoardTitle mutation (success, error)
- deleteBoard mutation (success, error)
- Cache invalidation after mutations

Files Created/Modified:
- src/__tests__/setup.ts - Added MSW server setup
- src/__tests__/utils/server-handlers.ts - MSW handlers for all endpoints
- src/__tests__/unit/hooks/useBoards.test.ts - 14 tests
- vitest.config.ts - Added test environment variables
- client/docs/client-testing/phase-2.md - Phase planning doc

Test Results: ✅ 14/14 useBoards tests passing
Next: useLists, useCards, useCardDetails, useCardFilters, useBulkActions

Phase 2 Status: ~20% complete (14/72+ tests)

Author: claude