- Add database migration for staff features (announcements, expenses,
courses, reviews, knowledge base, projects, marketplace, handbook)
- Add 8 new API endpoints: announcements, expenses, courses, reviews,
knowledge-base, projects, marketplace, handbook
- Update StaffAnnouncements.tsx to use real API with read tracking
- Update StaffExpenseReports.tsx to use real API with submit dialog
More staff pages to be updated in next commit.
