FINERACT-2836: Isolate Due Savings Charge Failures

[rhopman]

The Pay Due Savings Charges job previously processed all due charges in one shared transaction. If one account had insufficient funds, the job failed and rolled back successful charge collections for unrelated funded accounts.

This change processes each due savings charge in an independent transaction. Successful collections remain committed while failures are recorded with charge and account context, and the job continues processing the remaining charges before reporting the overall failure.

Tests cover mixed funded and insufficient-balance accounts, successful balance and charge updates, failure isolation, all-success behavior, and prevention of duplicate collection on rerun.

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