fix: address Phase 1-2 audit findings

- CORS: replace permissive() with configurable whitelist (default.toml)
- Auth store: synchronously restore state at creation to eliminate
  flash-of-login-page on refresh
- MainLayout: menu highlight now tracks current route via useLocation
- Add extractErrorMessage() utility to reduce repeated error parsing
- Fix all clippy warnings across 4 crates (erp-auth, erp-config,
  erp-workflow, erp-message): remove unnecessary casts, use div_ceil,
  collapse nested ifs, reduce function arguments with DTOs

crates/erp-auth/src/handler/user_handler.rs

@@ -31,7 +31,7 @@ where
 
     let page = pagination.page.unwrap_or(1);
     let page_size = pagination.limit();
-    let total_pages = (total + page_size - 1) / page_size;
+    let total_pages = total.div_ceil(page_size);
 
     Ok(Json(ApiResponse::ok(PaginatedResponse {
         data: users,