Credit workspaces for onboarding invite-team signups (#22309)

https://github.com/user-attachments/assets/6591cbb0-2b60-4f25-8b03-26b0da73f0d8

After the invite has been accepted:
<img width="1606" height="286" alt="CleanShot 2026-06-30 at 11 24 47@2x"
src="https://github.com/user-attachments/assets/7becf8a5-04dc-4512-ac7f-951a77e4c0ac"
/>

Adds a dedicated `ONBOARDING_INVITATION_TOKEN` app-token type so
invitations sent during the onboarding invite-team step are
distinguished from regular invites. When an invited person actually
signs up, the inviting workspace is credited 0.5 credits.

Reward eligibility is derived entirely server-side, with no public API
parameter: an invitation is reward-eligible only while the workspace is
in the onboarding invite-team step (`ONBOARDING_INVITE_TEAM_PENDING`), a
flag set once at workspace creation that no public mutation can re-arm.
Both token types stay valid invitations everywhere via a shared
`INVITATION_APP_TOKEN_TYPES`, so invitees still join normally and appear
in invite lists.

Crediting is a best-effort direct call to
`BillingCreditService.creditWorkspaceBalance` from the sign-in-up flow:
it no-ops when billing is disabled and never blocks signup, and is
bounded by a 10-invite-per-workspace cap. No DB migration needed:
`appToken.type` is a text column.

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packages/twenty-server/src/engine/core-modules/app-token/app-token.entity.ts

@@ -26,6 +26,7 @@ export enum AppTokenType {
   AuthorizationCode = 'AUTHORIZATION_CODE',
   PasswordResetToken = 'PASSWORD_RESET_TOKEN',
   InvitationToken = 'INVITATION_TOKEN',
+  OnboardingInvitationToken = 'ONBOARDING_INVITATION_TOKEN',
   EmailVerificationToken = 'EMAIL_VERIFICATION_TOKEN',
   EnterpriseValidityToken = 'ENTERPRISE_VALIDITY_TOKEN',
 }