Explains why the delivery fee specifically never changed while other
address info (label, street) updated fine after the previous fix:
AddAddressFormView only sets latLong when the CEP lookup happens to
return coordinates (AddAddressFormView.swift:141-146) — plenty of saved
addresses have none. Without coordinates the backend can't distinguish
that address from the previous one, so the fee (and, in Checkout,
checkoutAddressWatchKey itself) never actually changes, without any
error surfacing since it likely falls back to some default fee instead
of rejecting.
Added LocationService.geocodeAddress(street:number:neighborhood:city:
state:zip:), a thin CLGeocoder wrapper, and call it in both
CartView.refreshDeliveryFee and CheckoutView+Logic.
validateDeliveryAddressIfNeeded whenever coordinates are missing,
persisting the result back into appState.address so it doesn't need to
re-geocode on every subsequent check.
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