Refactor controllers to remove unnecessary return statements after JSON responses

- Removed redundant return statements in various controller functions across the dashboard module.
- This change improves code readability and maintains the same functionality.

internal/controllers/api/customer_controller.go

@@ -26,5 +26,4 @@ func CustomerPostSession_exchange(ctx *gin.Context) {
 		return
 	}
 	httpx.WriteJSON(ctx, resp)
-	return
 }