Cardano Updates

    Closed ──PartialFanout──────────► FanoutProgress
    FanoutProgress ──PartialFanout──► FanoutProgress  (repeat)
    FanoutProgress ──FinalPartialFanout──────────────► Final (burns tokens)
    Closed ──Fanout──────────────────────────────────► Final (≤ threshold, unchanged)

  Off-chain, HeadLogic.emitNextFanoutStep now distinguishes FreshFanout from
  FanoutInProgress to select the correct tx builder at each step.

    Closed ──PartialFanout──────────► FanoutProgress
    FanoutProgress ──PartialFanout──► FanoutProgress  (repeat)
    FanoutProgress ──FinalPartialFanout──────────────► Final (burns tokens)
    Closed ──Fanout──────────────────────────────────► Final (≤ threshold, unchanged)

  Off-chain, HeadLogic.emitNextFanoutStep now distinguishes FreshFanout from
  FanoutInProgress to select the correct tx builder at each step.

checkPartialFanout now verifies that headInValue equals headOutValue plus the sum of all distributed output values, preventing Ada theft via outputs not counted by the membership proof. The off-chain partialFanoutTx builder is updated accordingly to subtract distributed values from the continuing head output.

Got all changes from the capi-10.21 branch here

Signed-off-by: Sasha Bogicevic <[email protected]>

Optimizations applied:
 * Single-pass serialization: each 'TxOut' is serialized once via
   @serialiseData . toBuiltinData@ and reused for both UTxO hash checks
   and accumulator scalar computation.
 * Combined CRS lookup: the reference input for the CRS is looked up once
   and decoded only when the membership check is actually reached.

Signed-off-by: Sasha Bogicevic <[email protected]>