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/routers/__init__.py

@@ -1,5 +1,6 @@
 from .address import address_router
 from .contact import contact_router
+from .local_contact import local_contact_router
 from .proposal import router as proposal_router
 from .dewar import dewar_router
 from .shipment import shipment_router
@@ -9,6 +10,7 @@ from .protected_router import protected_router as protected_router
 __all__ = [
     "address_router",
     "contact_router",
+    "local_contact_router",
     "proposal_router",
     "dewar_router",
     "shipment_router",