TezosWithdrawOperation records created in on_rollup_execute were always
persisted with amount=NULL, so bridge_operation.withdrawal.l1_transaction.amount
was missing via GraphQL for classic XTZ and FA withdrawals as well as for
fast-withdrawal service-provider reimbursements. Extract the L1-native amount
from the outbox message's ticket payload and store it on the L1 record.

Also cache the two outbox Michelson types at module level to avoid
recompiling them on every parse; reused in OutboxParametersHash as well.

Assisted-By: claude-opus-4-7[1m]