Add endpoint for creating local contacts with access control

Introduced a new `local_contact_router` to handle creation of local contacts. The endpoint enforces role-based access control and ensures no duplication of email addresses. Updated the router exports for consistency and cleaned up a large test file to improve readability.

backend/app/data/__init__.py

@@ -9,6 +9,8 @@ from .data import (
     dewar_types,
     serial_numbers,
     sample_events,
+    local_contacts,
+    beamtimes,
 )
 from .slots_data import slots
 
@@ -24,4 +26,6 @@ __all__ = [
     "serial_numbers",
     "sample_events",
     "slots",
+    "local_contacts",
+    "beamtimes",
 ]