refactor: 重構模組通訊與調整儀表板功能

- 依循跨模組通訊規範，將 Sales 與 Production 模組中對 Inventory 的直接模型關聯改為透過 InventoryServiceInterface 取得
- 於 InventoryService 實作獲取最高庫存價值、即將過期商品等方法，供儀表板使用
- 確保所有跨模組調用皆採用手動水和（Manual Hydration）方式組合資料
- 移除本地已歸檔的 .agent 規範檔案

app/Modules/Inventory/Contracts/InventoryServiceInterface.php

@@ -40,6 +40,14 @@ interface InventoryServiceInterface
      */
     public function getProductsByIds(array $ids);
 
+    /**
+     * Get multiple warehouses by their codes.
+     * 
+     * @param array $codes
+     * @return \Illuminate\Support\Collection
+     */
+    public function getWarehousesByCodes(array $codes);
+
     /**
      * Search products by name.
      * 
@@ -139,4 +147,14 @@ interface InventoryServiceInterface
      * @return object
      */
     public function findOrCreateWarehouseByName(string $warehouseName);
+
+    /**
+     * Get top inventory value for dashboard.
+     */
+    public function getTopInventoryValue(int $limit = 5): \Illuminate\Support\Collection;
+
+    /**
+     * Get items expiring soon for dashboard.
+     */
+    public function getExpiringSoon(int $limit = 5): \Illuminate\Support\Collection;
 }