Flaky test: tests/sentry/deletions/tasks/test_hybrid_cloud.py::TestCrossDatabaseTombstoneCascadeBehavior::test_cross_db_deletion

Failing test: `tests/sentry/deletions/tasks/test_hybrid_cloud.py::TestCrossDatabaseTombstoneCascadeBehavior::test_cross_db_deletion`
Sentry sha: 02e8ded902342f5b18db32c91f8f4f174afc4551
Run: https://github.com/getsentry/sentry/actions/runs/22243447656

```
.venv/lib/python3.13/site-packages/django/db/backends/utils.py:105: in _execute
return self.cursor.execute(sql, params)
src/sentry/db/postgres/decorators.py:16: in inner
return func(self, *args, **kwargs)
src/sentry/db/postgres/base.py:95: in execute
return self.cursor.execute(sql, params)
E psycopg2.errors.UniqueViolation: duplicate key value violates unique constraint "sentry_monitor_pkey"
E DETAIL: Key (id)=(9) already exists.

The above exception was the direct cause of the following exception:
tests/sentry/deletions/tasks/test_hybrid_cloud.py:409: in test_cross_db_deletion
Monitor.objects.create(
src/sentry/silo/base.py:158: in override
return original_method(*args, **kwargs)
.venv/lib/python3.13/site-packages/django/db/models/manager.py:87: in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
src/sentry/silo/base.py:158: in override
return original_method(*args, **kwargs)
.venv/lib/python3.13/site-packages/django/db/models/query.py:665: in create
obj.save(force_insert=True, using=self.db)
src/sentry/silo/base.py:158: in override
return original_method(*args, **kwargs)
src/sentry/monitors/models.py:298: in save
return super().save(*args, **kwargs)
.venv/lib/python3.13/site-packages/django/db/models/base.py:902: in save
self.save_base(
src/sentry/silo/base.py:158: in override
return original_method(*args, **kwargs)
.venv/lib/python3.13/site-packages/django/db/models/base.py:1008: in save_base
updated = self._save_table(
.venv/lib/python3.13/site-packages/django/db/models/base.py:1169: in _save_table
results = self._do_insert(
.venv/lib/python3.13/site-packages/django/db/models/base.py:1210: in _do_insert
return manager._insert(
.venv/lib/python3.13/site-packages/django/db/models/manager.py:87: in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
.venv/lib/python3.13/site-packages/django/db/models/query.py:1873: in _insert
return query.get_compiler(using=using).execute_sql(returning_fields)
.venv/lib/python3.13/site-packages/django/db/models/sql/compiler.py:1882: in execute_sql
cursor.execute(sql, params)
.venv/lib/python3.13/site-packages/django/db/backends/utils.py:122: in execute
return super().execute(sql, params)
.venv/lib/python3.13/site-packages/sentry_sdk/utils.py:1870: in runner
return original_function(*args, **kwargs)
.venv/lib/python3.13/site-packages/django/db/backends/utils.py:79: in execute
return self._execute_with_wrappers(
.venv/lib/python3.13/site-packages/django/db/backends/utils.py:92: in _execute_with_wrappers
return executor(sql, params, many, context)
src/sentry/db/postgres/base.py:70: in _execute__include_sql_in_error
return execute(sql, params, many, context)
src/sentry/db/postgres/base.py:58: in _execute__clean_params
return execute(sql, clean_bad_params(params), many, context)
src/sentry/testutils/hybrid_cloud.py:133: in __call__
return execute(*params)
.venv/lib/python3.13/site-packages/django/db/backends/utils.py:100: in _execute
with self.db.wrap_database_errors:
.venv/lib/python3.13/site-packages/django/db/utils.py:91: in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
.venv/lib/python3.13/site-packages/django/db/backends/utils.py:105: in _execute
return self.cursor.execute(sql, params)
src/sentry/db/postgres/decorators.py:16: in inner
return func(self, *args, **kwargs)
src/sentry/db/postgres/base.py:95: in execute
return self.cursor.execute(sql, params)
E django.db.utils.IntegrityError: duplicate key value violates unique constraint "sentry_monitor_pkey"
E DETAIL: Key (id)=(9) already exists.
E 
E SQL: INSERT INTO "sentry_monitor" ("id", "date_added", "organization_id", "project_id", "status", "guid", "slug", "name", "is_upserting", "owner_user_id", "owner_team_id", "config") VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s) RETURNING "sentry_monitor"."id", "sentry_monitor"."is_upserting"
```

Start by running tests/sentry/deletions/tasks/test_hybrid_cloud.py::TestCrossDatabaseTombstoneCascadeBehavior::test_cross_db_deletion and read its setup around line 409. Trace how the test creates Monitor records and how the hybrid-cloud database state leads to the duplicate sentry_monitor primary key. Done means the test passes reliably without the reported IntegrityError.

Written by the indexing model from the issue text.