FINERACT-2834: Expose the originating client charge ID on client payment transactions

[rhopman]

This change exposes clientChargeId in client transaction API responses. The existing SQL query already retrieves the originating client charge ID, but the row mapper previously discarded it before constructing ClientTransactionData.

The existing client transaction integration test now verifies that a charge-payment transaction returns the ID of the client charge it paid. This allows consumers to correlate payments with exact client charges without relying on names, amounts, or other potentially ambiguous attributes.

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