refactor(api): split Axum handlers into handler/service/repo modules

Keep the REST contract; move domain logic out of route files so checkout, fulfillment, and identity can be reused across customer, shop, and admin surfaces.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/api/src/lib.rs

@@ -1,11 +1,10 @@
 pub mod auth;
-pub mod cart;
 pub mod config;
 pub mod error;
+pub mod http;
 pub mod models;
 pub mod money;
-pub mod pagination;
-pub mod routes;
+pub mod modules;
 pub mod seed;
 pub mod state;
 
@@ -16,8 +15,8 @@ use crate::state::AppState;
 
 pub fn build_router(state: AppState) -> Router {
     Router::new()
-        .route("/api/health", get(routes::health::health))
-        .nest("/api", routes::api_router(state.clone()))
+        .route("/api/health", get(modules::health::health))
+        .nest("/api", modules::api_router())
         .layer(TraceLayer::new_for_http())
         .layer(CorsLayer::permissive())
         .with_state(state)