fix(userflags): read the fee override from its own field

[bmc08gt]

UserFlags.resolve() passed overrides.newCurrencyPurchaseAmount to both newCurrencyPurchaseAmount and newCurrencyFeeAmount. In the debug flag editor that meant overriding the new-currency fee amount did nothing, and overriding the new-currency purchase amount silently changed the fee amount too.

Overrides.newCurrencyFeeAmount was already declared, defaulted in Overrides.None, read from preferences via prefs.readOverride(Field.NewCurrencyFeeAmount), and registered as an editable entry in the flags UI — it just had no consumer.

The two fields use distinct preference keys, so no stored data needs migrating: a fee override set before this change was written correctly and simply ignored, and now takes effect.

Tests

The module had ResolvedFlagTest and FieldOverrideTest, but nothing exercised resolve() itself, which is how this got through. ResolvedUserFlagsTest drives a table of all ten overridable fields against a server-flags fixture with distinct values:

• each override applied on its own lands on its own resolved field and leaves the other nine unoverridden and at their server value;
• all ten applied together each land on their own field;
• with Overrides.None, every resolved field reports its server value — this also pins the server-side mapping, including minimumHolderValue → minimumHolderAmountForLeaderboard and the OnRampProvider.Defined filtering;
• a reflection check over Overrides' declared fields fails if a new override is added without a case, so the table can't fall behind.

Reverting the one-word fix fails the table with overriding newCurrencyPurchaseAmount also overrode newCurrencyFeeAmount.