feat(currency-creator): fund currency launches with any currency

[bmc08gt]

Lets a new currency be created paying with USDF or another launchpad currency (a treasury-funded cross-currency swap), rather than USDF reserves only.

UI

• New funding-source token picker step in the create flow. Its own top bar is suppressed inside the flow to avoid stacking two bars.
• "Ready To Create?" confirmation modal before payment (ConfirmPurchase → modal → launch).
• The intro balance gate now checks any held currency: no balance at all → "No Balance Yet"; some balance but none covers the cost → "Insufficient Balance".

Service layer (opencode)

• launchToken mints and funds in one call, routing on the funding token:
  • USDF → a plain buy of the freshly-launched stub.
  • any other launchpad currency → the treasury-funded cross-currency swap that creates and funds the new currency in a single transaction.
• Made the public swap API explicit: the overloaded crossCurrencySwap (which switched modes on a nullable fullAmountExchangeData) is split into swap (existing-currency swaps) and launchToken (new-currency treasury launch). The internal exchange-data type no longer leaks into the app-facing interface.
• TokenCreateRequest carries a Funding describing how the launch is paid for; the service decides buy vs. swap and builds the exchange data from it.

Server contract (treasury swap)

The new-currency swap's full_amount_exchange_data and the funding intent are validated against the ocp-server rules: quarks are funding-token quarks (the reserve sells them), native_amount is the exact USD launch cost in USD, and the fee is likewise funding-token quarks valued at its USD amount. A small VerifiedFiat.valuedAt(...) helper pins the native to the exact cost (kept in the transaction controller so the exchange-data construction is self-contained).