Register an account's deposit receivers

Answers, and keeps, the receivers a deposit to intent_account in NEAR Intents carries on its source chain: deposit_hash, base58 of sha256 of {"account_id":"intents.near","msg":"{\"receiver_id\":\"<account>\"}"} (what omni rebuilds), and legacy_hash, base58 of sha256("intents.near" ‖ msg) (old deposits). The backend’s auto_deposit_register. The account is normalized: an EVM address or a NEAR account is lowercased, a base58 32-byte key (a Solana address) becomes its hex implicit account. Without the database, the hashes are still answered with status: not_recorded.