fix: Replace str with string in types

frontend/lib/types.ts

@@ -1,12 +1,12 @@
 export type TenderItem = {
-  name: str;
+  name: string;
   quantity: number;
-  unit: str;
+  unit: string;
 };
 
 export type TenderAttachment = {
-  name: str;
-  url: str;
+  name: string;
+  url: string;
 };
 
 export type Tender = {