Function compute_minimum_shielded_fee 

pub fn compute_minimum_shielded_fee(
    num_actions: usize,
    platform_version: &PlatformVersion,
) -> Credits

Computes the minimum fee (in credits) for a shielded state transition.

The fee formula mirrors the on-chain validation in validate_minimum_shielded_fee: min_fee = proof_verification_fee + num_actions × (processing_fee + storage_fee)

where storage_fee = SHIELDED_STORAGE_BYTES_PER_ACTION × (disk + processing) credits/byte.

Parameters

• num_actions — number of Orchard actions in the bundle
• platform_version — protocol version (determines fee constants)