Remove all @firebase/util imports, replace uuidv4 with crypto.randomUUID

- Create src/utils/uuid.ts utility using crypto.randomUUID()
- Replace all uuidv4 imports from @firebase/util across 11 component files
- Replace base64 import in paypal.ts with Buffer-based implementation

Made-with: Cursor

src/utils/paypal.ts

@@ -1,5 +1,5 @@
 import {TokenError, TokenSuccess} from "@/interfaces/paypal";
-import {base64} from "@firebase/util";
+const base64 = { encodeString: (s: string) => Buffer.from(s).toString("base64") };
 import axios from "axios";
 
 export const getAccessToken = async () => {