Feat/circuit version in memo

[nol4lej]

Move a shielded note's ZK circuit version into the encrypted memo plaintext, so a note is self-contained: a wallet that recovers a note by scanning the chain keeps its true circuit version without any indexer lookup. This keeps old notes spendable across a VK rotation, the prover/pallet verify a spent note against the exact circuit version that created it, not the active one.
Before, the version had no on-chain home in the note itself; it was inferred from the indexer feed. Now it rides in the memo alongside value/assetId/blinding.

Changes

orbinum-encrypted-memo 0.6.0 → 0.7.0

• MemoData gains circuit_version: u32 as the last plaintext field.
• Plaintext 116 → 120 bytes; encrypted wire format 176 → 180 bytes (nonce(12) | ciphertext(120) | MAC(16) | ephPk(32)).
• MemoData::new / new_without_counterparty gain a trailing circuit_version arg.

pallet-shielded-pool 0.9.0 → 0.10.0

• MAX_ENCRYPTED_MEMO_SIZE 176 → 180; EncryptedMemo slice offsets updated (ciphertext [12..132], tag [132..148], ephPk [148..180]). The pallet still treats the memo as opaque bytes.
• Weights regenerated on the reference host (ubuntu-32gb-fsn1-1, AMD EPYC-Genoa): CommitmentMemos MaxEncodedLen 226 → 230 raises proof_size for shield, shield_batch, private_transfer, unshield, claim_shielded_fees.

Runtime

• spec_version 5 → 6.
• transaction_version unchanged (3): the extrinsic SCALE codec is identical, the memo arg is still BoundedVec, only its max bound rose, so offline-signed extrinsics decode the same.