feat: add pattern validation for amount input field

- Add pattern="[0-9]+(\.[0-9]{1,2})?" to prevent invalid input
- Browser now validates number format before submission
- Improves UX by catching errors earlier

lib/mv_web/live/membership_fee_type_live/form.ex

@@ -46,6 +46,7 @@ defmodule MvWeb.MembershipFeeTypeLive.Form do
           label={gettext("Amount")}
           step="0.01"
           min="0"
+          pattern="[0-9]+(\.[0-9]{1,2})?"
           required
         />