add ironwood pool processing

[alexqrid]

Summary

Adds processing for Ironwood, the new Zcash shielded pool introduced in
the NU6.3 network upgrade (mainnet activation at block 3,428,143, ~2026-07-28).
Ironwood is the successor to Orchard — built on revised Orchard code with
formal verification — and its transaction bundle mirrors Orchard's
(actions + valueBalanceZat), so the handling follows the existing
Orchard path.

Changes (Modules/Common/UTXOMainModule.php)

• Count ironwood actions in the "no events for transaction" guard so
  Ironwood-only transactions aren't rejected.
• Emit an ironwood-pool value-change event from transaction['ironwood']
  (negated valueBalanceZat) and fold it into the transaction fee, matching
  the Orchard logic. Sorted at PHP_INT_MAX - 1, immediately after Orchard.
• Add ironwood to the per-block pool reconciliation: include it in
  $this_pools, accumulate ironwood-pool effects, and subtract it from the
  transparent pool so the valuePools/chainSupply delta checks stay exact.

Notes

• The Ironwood pool is zero until NU6.3 activates, so behavior is unchanged
  on pre-activation blocks.
• The Orchard→Ironwood turnstile migration surfaces purely as pool value
  deltas and is covered by the existing reconciliation checks.
• The transaction field name (ironwood) is assumed from the revised-Orchard
  structure since the published RPC docs (v6.12.2) predate NU6.3