feat(pswap): add min_fill_amount to PswapNoteStorage

[Sertug17]

Summary

Adds an optional min_fill_amount field to PswapNoteStorage, allowing PSWAP note creators to set a minimum fill threshold. This prevents griefing via tiny partial fills that produce dust P2ID payback notes.

Changes

• Added min_fill_amount: Option to PswapNoteStorage with bon::Builder support
• Fixed creator_account_id serialization order from [prefix, suffix] to [suffix, prefix]
• Updated From/TryFrom implementations for the new 7-element storage layout
• Added min_fill_amount check in MASM execute_pswap with ERR_PSWAP_FILL_BELOW_MINIMUM error
• Updated NUM_STORAGE_ITEMS from 6 to 7 in MASM
• Added tests for roundtrip serialization with the new field

Storage Layout

Slot	Field
[0]	Requested asset faucet ID suffix
[1]	Requested asset faucet ID prefix
[2]	Requested asset amount
[3]	Payback note type
[4-5]	Creator account ID (suffix, prefix)
[6]	min_fill_amount (0 = None)

Related Issues

• Fixes PSwap: User should be able to set minimum amount that can be filled in a note. #3203
• Related to bug: PSWAP note_fill payout share is never transferred on full/over fill offered asset is destroyed #3169 (dust fragmentation from tiny partial fills)

Checklist

• cargo check -p miden-standards passes
• cargo test -p miden-standards pswap passes (8/8 tests)
• MASM side implementation (follow-up PR)

Notes

The MASM pswap.masm script now includes the min_fill_amount check in execute_pswap. If fill_amount < min_fill_amount (and min_fill_amount != 0), the transaction aborts with ERR_PSWAP_FILL_BELOW_MINIMUM.

[Sertug17]

@VAIBHAVJINDAL3012 @partylikeits1983 @PhilippGackstatter

This PR is now ready for review. It includes both the Rust and MASM implementations discussed in #3203:

Rust side:

• min_fill_amount: Option<u64> added to PswapNoteStorage
• Creator ID serialization order fixed ([prefix, suffix] → [suffix, prefix])
• From/TryFrom updated for 7-element storage layout
• Tests added

MASM side:

• NUM_STORAGE_ITEMS updated from 6 → 7
• min_fill_amount check in execute_pswap with ERR_PSWAP_FILL_BELOW_MINIMUM
• Creator ID order fixed in MASM as well

All 8 pswap tests pass. Let me know if you'd like any changes!