Create Postman collection for Cboard Access admin

[magush27]

Create a Postman collection for testing and administering Cboard Access clients.

File: postman/CboardAccess.collection.json

Tasks:

• Define environment variables (API_URL, AUTH_TOKEN)
• Create request: Create Access client
• Create request: List all clients
• Create request: Update client
• Create request: Deactivate client
• Create request: View statistics
• Create request: Test public client listing
• Create request: Test public board access