feat(phase-4b): backend business-logic, 8 entities, 32 endpoints, 58 tests

app/services/__init__.py

@@ -1 +1,8 @@
-"""Business logic service layer."""
+"""Service layer for the CRM system.
+
+Submodules are imported directly by routers via
+`from app.services.<name> import <func>` to avoid circular-import issues
+during application startup.
+"""
+
+__all__: list[str] = []