fix: Stellar amount and fee display format

Author: muzaffarbhat07

apps/stellar_app/stellar_txn.c

@@ -451,7 +451,7 @@ static bool get_user_verification(void) {
   char amount_string[30] = {'\0'};
   double decimal_amount = (double)decoded_txn->operations[0].amount;
   decimal_amount *= 1e-7;    // Convert stroops to XLM
-  snprintf(amount_string, sizeof(amount_string), "%.*g", 7, decimal_amount);
+  snprintf(amount_string, sizeof(amount_string), "%.7f", decimal_amount);
 
   char display[100] = {'\0'};
   snprintf(display,
@@ -468,7 +468,7 @@ static bool get_user_verification(void) {
   char fee_string[30] = {'\0'};
   double decimal_fee = (double)decoded_txn->fee;
   decimal_fee *= 1e-7;    // Convert stroops to XLM
-  snprintf(fee_string, sizeof(fee_string), "%.*g", 7, decimal_fee);
+  snprintf(fee_string, sizeof(fee_string), "%.7f", decimal_fee);
 
   char fee_display[50] = {'\0'};
   snprintf(fee_display,