Update all database session dependencies to use get_db

main.py

@@ -66,7 +66,7 @@ async def process_call(
     caller_number: str = Form(...),
     called_number: str = Form(...),
     customer: Customer = Depends(verify_api_key),
-    db: Session = Depends(Customer.get_db)
+    db: Session = Depends(get_db)
 ):
     """
     Process a voice call recording file.
@@ -138,7 +138,7 @@ async def process_call(
 @app.get("/api/v1/calls/{customer_id}")
 async def list_calls(
     customer_id: int,
-    db: Session = Depends(Customer.get_db),
+    db: Session = Depends(get_db),
     current_admin: str = Depends(get_current_admin)
 ):
     """
@@ -182,7 +182,7 @@ async def login_for_access_token(form_data: OAuth2PasswordRequestForm = Depends(
 @app.post("/api/v1/customers/", response_model=Customer)
 async def create_customer(
     customer: Customer,
-    db: Session = Depends(Customer.get_db),
+    db: Session = Depends(get_db),
     current_admin: str = Depends(get_current_admin)
 ):
     """Create new customer"""