chore: remove unused SWAP and MINT attachments

[PhilippGackstatter]

Removes unused attachment fields from SwapNoteStorage and MintNoteStorage.

Summary

• Remove payback_attachment: NoteAttachment from SwapNoteStorage and the corresponding payback_note_attachment parameter from SwapNote::create
• Remove attachment: NoteAttachment from both MintNoteStorage::Private and MintNoteStorage::Public variants, along with the with_attachment() method
• Update SWAP and MINT MASM note scripts to remove attachment storage/loading and output_note::set_attachment calls
• Reorder storage layouts to maintain word-aligned addresses for mem_loadw_le / mem_storew_le operations

Motivation

These attachment fields were always set to NoteAttachment::default() and never used. Removing them simplifies the storage layout and reduces the note storage size.

Note: The metadata attachment on the note (e.g. swap_note_attachment in SwapNote::create, attachment in MintNote::create) is not removed — only the redundant attachment fields stored inside the note storage.

This also makes the multiple note attachments PR easier to update.

part of #2555