test: Improve create teams handler tests (calcom#25213)

I am refactoring create teams handler to a service in another PR - thought we should improve the test in the mean time.

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## Summary by cubic
Expand and restructure tests for createTeamsHandler to cover auth, org/slug validation, team creation and migration, redirects, credits, invites, and subscriptions. This improves reliability ahead of the service refactor.

- **Refactors**
  - Rewrote tests into scenario-based suites for Authorization, Organization Validation, Slug Validation, Team Creation/Migration, Redirects, and Edge Cases.
  - Added helpers (createTestProfile, flexible createScenario/createTestMembership) and organization/profile support to model slug collisions.
  - Assert TRPCError codes/messages and redirect records; cover platform orgs, unpublished/non-existent teams, and empty names.
  - Mocked Stripe subscription cancel and inviteMembersWithNoInviterPermissionCheck; verified credit transfer and owner memberships.

<sup>Written for commit 8c216c6. Summary will update automatically on new commits.</sup>

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Author: sean-brydon