feat: add login/logout/status commands

[pratik50]

Summary

• Removed auto-created demo profile
• Added pb login / logout / status
• Now user must login first before running stream/query/etc

Why

Earlier pb was automatically using demo.parseable.com as default profile.
That demo server is removed, so commands were failing.
Now pb works only after proper authentication.

Changes

• Removed defaultInitialProfile() logic (no auto demo config anymore)
• Added pb login
  • supports --token (cloud)
  • supports --url + --username + --password (self-hosted)
• Added pb logout
• Added pb status (checks /about endpoint)
• Config updated: Profile now supports Token
• HTTP client updated:
  • Token → Bearer auth
  • Username/password → Basic auth

Test

Self-hosted

• pb login --url http://localhost:8000 --username <username> --password <password>
• pb status
• pb stream list
• pb logout

Cloud token flow ------- (not tested yet, will checkout with Agent workflow)

• pb login --token <token>
• pb status
• pb stream list