feat: encrypted account send via ZK proofs

[n13]

Summary

Makes encrypted (wormhole) accounts spendable. An encrypted account is one HD sequence of wormhole addresses (m/44'/189189189'/0'/0'/n') treated as a single UTXO pool:

• Send: coin selection picks unspent UTXOs (largest-first, 7 leaf proofs per aggregated batch), pays the recipient via exit slot 1 and returns change to a fresh address via exit slot 2 of the last leaf — no linkage between deposits and spends. Packaged as an EncryptedSendStrategy so the shared recipient/amount/review screens are untouched.
• Receive: the Receive screen rotates to the next unused address (linear with change addresses), so deposits aren't linkable to each other.
• Recovery: gap-limit scan (same algorithm as transparent accounts, batched indexer queries) rediscovers all funds from the mnemonic alone; runs automatically on wallet import.
• In-flight consistency: spent nullifiers + pending change are persisted per batch, so balances stay exact mid-send and back-to-back sends can't double-select inputs.

WormholeClaimService is generalized into WormholeSendService (per-leaf output assignments); mining-rewards claim becomes a wrapper over it, shared with the miner app. Rust ProofInput now exposes exit_account_2/output_amount_2.

Feature-flag gated by enableEncryptedAccount.

Test plan

• quantus_sdk unit tests incl. new coin-selection suite (fee/quantization/batch-minimum/multi-batch cases)
• dart analyze clean on quantus_sdk, mobile-app, miner-app
• Manual: send from encrypted account (single & multi-batch), verify change lands on fresh address and balance refreshes
• Manual: wipe + reimport wallet, verify encrypted funds are rediscovered
• Manual: miner-app claim rewards regression