test: RgbSettlementModule existence + exact-amount checks

[sh3ifu]

Summary

Test branch for the RgbSettlementModule beforeFundsOut rework (fix PR:
rgb-opid-amount-binding). beforeFundsOut is now a view proof-of-mint check
that decodes (uint256[] operationIds, uint256[] amounts) and asserts every
id exists in fundsInRecords with an exactly matching amount — no
consumption, no tie to fundsOut.amount. Solvency/replay remain owned by
Bridge.lockedLiquidity + consumedBurnIds.

Changes

• RgbSettlementModule.t.sol fully rewritten: existence + exact-amount happy
  paths (records left intact), reverts for AmountMismatch (over/under),
  SettlementDataLengthMismatch, mid-array mismatch; empty-array, duplicate-id
  (harmless), repeated-call view stability; exact-match-only fuzz.
• Bridge / Integration / MultisigProxy: switched settlementData to the
  two-array encoding, replaced FundsOutAmountExceedsFundsIn assertions with
  AmountMismatch, and replaced all "record consumed/residual" assertions with
  "record unchanged" (permanent proof-of-mint ledger).
• Bridge settlement builders are pure (encode AMOUNT, or explicit amounts for
  seeded/fuzz/mismatch records) so they don't consume vm.prank/vm.expectRevert
  when passed inline.