Allow deletion of legacy suspended organizations

[niemyjski]

What changed

Clear suspension metadata before saving a soft-deleted organization.

Why

Organizations persisted by older billing flows can contain a short system marker in SuspendedByUserId. The current model correctly requires object-ID-shaped user IDs, but deleting one of these legacy suspended organizations re-saved the record and returned HTTP 422 instead of completing the deletion.

Verification

• Added an integration regression test that seeds a synthetic legacy persisted marker through the isolated Elasticsearch test client.
• Confirmed the regression reproduced as HTTP 422 before the fix.
• Confirmed the same test passes after the fix and the organization is no longer retrievable.
• dotnet build Exceptionless.slnx --no-restore -m:1
• OrganizationEndpointTests: 104/104 passed

No production identifiers or customer data are included.

[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
Exceptionless.Insulation	37%	35%	286	❌
Exceptionless.Core	75%	67%	10012	➖
Exceptionless.Web	85%	69%	7033	✔
Exceptionless.AppHost	38%	40%	139	❌
Summary	78% (23525 / 30333)	67% (11041 / 16544)	17470	✔