Add project creation from team dashboard and update seed data

- Add project creation modal to TeamDashboardPage with team_id assignment
- Update createProject API function to accept optional team_id
- Update seed data to create a "Demo Team" and assign all projects to it
- Admin user is added as team owner when present

CHANGELOG.md

@@ -38,10 +38,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - TeamContext provider for managing current team selection
   - TeamSelector dropdown component (persists selection in localStorage)
   - Teams list page at `/teams`
-  - Team dashboard page at `/teams/{slug}`
+  - Team dashboard page at `/teams/{slug}` with inline project creation
   - Team settings page at `/teams/{slug}/settings`
   - Team members page at `/teams/{slug}/members`
   - Teams navigation link in header (authenticated users only)
+- Updated seed data to create a "Demo Team" and assign all seed projects to it
 - Added TypeScript types and API client functions for teams
 - Added integration tests for team CRUD, membership, and project operations
 - Added unit tests for TeamAuthorizationService