feat: Add /sell command, enhance inventory service, and refactor student ID card generation with new constellation graphics and dynamic backgrounds.

src/modules/inventory/inventory.service.ts

@@ -120,5 +120,11 @@ export const inventoryService = {
         };
 
         return tx ? await execute(tx) : await DrizzleClient.transaction(execute);
-    }
+    },
+
+    getItem: async (itemId: number) => {
+        return await DrizzleClient.query.items.findFirst({
+            where: eq(items.id, itemId),
+        });
+    },
 };