Restructure crates for correct proc macro usage

Signed-off-by: Lee Smet <lee.smet@hotmail.com>

heromodels/examples/simple_model_example.rs

@@ -1,6 +1,6 @@
-use heromodels::model;
-use heromodels::models::core::model::{BaseModelData, Model, IndexKey};
-use serde::{Serialize, Deserialize};
+use heromodels_core::{BaseModelData, Model};
+use heromodels_derive::model;
+use serde::{Deserialize, Serialize};
 
 // Basic usage
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -14,16 +14,17 @@ pub struct SimpleUser {
 fn main() {
     println!("Hero Models - Simple Model Example");
     println!("==================================");
-    
+
     // Example usage of the generated implementation
     println!("SimpleUser DB Prefix: {}", SimpleUser::db_prefix());
-    
+
     let user = SimpleUser {
         base_data: BaseModelData::new(1),
         login: "johndoe".to_string(),
         full_name: "John Doe".to_string(),
     };
-    
+
     println!("\nSimpleUser ID: {}", user.get_id());
     println!("SimpleUser DB Keys: {:?}", user.db_keys());
-}
+}
+