[react-query, learner-dashboard] Phase2: Redux → React Query

[jacobo-dominguez-wgu]

Phase 2: Redux → React Query

• Set up QueryClient with defaults
• Create inventory of slices to migrate (sub-issues)
• For each slice:
  • Extract API functions
  • Create query keys factory
  • Create custom hooks
  • Update components
  • Comment out Redux code
  • Write/update tests
  • Validation
    • All tests pass
    • Manual QA complete
    • Performance verified