approve/pay accepted any approved_rials/paid_rials with no bounds, so the
claiming tenant could write arbitrary figures into the insurer-debt ledger
(negative, or far above the claimed total). Validate: approved ∈ [0, claimed],
paid ∈ [0, approved] → 422 otherwise. (The "force arbitrary status" half of the
finding was already prevented by Claim::canTransitionTo.)
Regression: tests/Billing/ClaimAmountBoundsTest.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
