fix(db): purge insurance config when a doctor/clinic is deleted (H5)

tenant_insurances, entity_insurance_pricing and tenant_service_coverages
reference their owner through a polymorphic (entity_type, entity_id) pair, so no
database FK can cascade their cleanup. Hard-deleting a doctor (DoctorController)
or clinic (AdminApiController) left these rows orphaned.

Add TenantInsuranceCleanupService::purgeForEntity() and call it from both delete
paths — removes coverage (via owning tenant_insurance ids), then tenant
insurances, then pricing.

Residual (separate, lower-freq paths): deleting an insurance category or a
service_item still orphans rows that reference them by id — tracked under the
medium-tier soft-ref findings.

Regression: tests/Insurance/TenantInsuranceCleanupTest.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/api/admin.md

@@ -458,6 +458,8 @@ Delete a clinic.
 
 **Permission:** `ROLE_ADMIN`
 
+> **Side effect:** the clinic's insurance configuration (`tenant_insurances`, `entity_insurance_pricing`, and their `tenant_service_coverages`) is purged in the same request — polymorphic `entity_id`, cleaned up at the application level.
+
 ### Response `200`
 ```json
 { "success": true, "data": { "message": "کلینیک حذف شد" } }