Implement team-based organization for projects with role-based access control:
Backend:
- Add teams and team_memberships database tables (migrations 009, 009b)
- Add Team and TeamMembership ORM models with relationships
- Implement TeamAuthorizationService for team-level access control
- Add team CRUD, membership, and projects API endpoints
- Update project creation to support team assignment
Frontend:
- Add TeamContext for managing team state with localStorage persistence
- Add TeamSelector component for switching between teams
- Add TeamsPage, TeamDashboardPage, TeamSettingsPage, TeamMembersPage
- Add team API client functions
- Update navigation with Teams link
Security:
- Team role hierarchy: owner > admin > member
- Membership checked before system admin fallback
- Self-modification prevention for role changes
- Email visibility restricted to team admins/owners
- Slug validation rejects consecutive hyphens
Tests:
- Unit tests for TeamAuthorizationService
- Integration tests for all team API endpoints
