Add BRC-116 permission token codec

[rohenaz]

Summary

• add strict typed DPACP, DBAP, DCAP, and DSAP permission-token models
• encode/decode encrypted signed PushDrop locks using the BRC-116 admin protocol, key ID 1, self/forSelf, and TS-compatible lock-before layout
• verify the trailing signature and wallet-owned locking key, require authenticated decryption for every field, and strictly validate semantic fields
• fail closed with a typed field index on decryption failure; no plaintext token fallback is authoritative
• cover normative field order, baskets, crypto arguments, all token round trips, expiry boundaries, DCAP subset behavior, DSAP shape, validation failures, and a concrete DBAP field-boundary repartition attack

Verification

• swift test --filter PermissionTokenCodecTests (10 passed)
• swift test (219 executed, 10 expected live-test skips, 0 failures)

Security note

PushDrop signs the concatenation of fields, which does not commit to field boundaries. The DBAP adversarial test preserves the signed concatenation while moving a byte between ciphertext fields and proves authenticated per-field decryption rejects the collision.

Scope

Codec/models only. No repository, RemoteWallet adapter, manager, UI, or WalletInterface conformance.