[rewrite] Work on user registration, slightly polished schemas structure

frontend/src/pages/auth/sign-up/components/sign-up-form.tsx

@@ -33,9 +33,9 @@ const formSchema = z
 		phone_number: z
 			.string()
 			.min(1, { message: "Please enter your phone number" })
-			.min(10, { message: "Phone number must be at least 10 digits" })
+			.min(2, { message: "Phone number must be at least 2 digits" })
 			.max(15, { message: "Phone number cannot be longer than 15 digits" })
-			.regex(/^\+\d{1,3} \d{1,9}$/, { message: "Invalid phone number format" }),
+			.regex(/^\+[1-9]\d{1,14}$/, { message: "Invalid phone number format" }),
 		password: z
 			.string()
 			.min(1, { message: "Please enter your password" })