feat(wallet): implement wallet send with k256 signing

- Loads encrypted keystore, derives sender address from verifying key
- Fetches current nonce via nu_getAccount RPC
- Builds TokenTransfer payload, signs SHA-256(tx_id) with secp256k1
- Broadcasts via nu_sendRawTx, prints returned tx_id
- Add sha2 dependency

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Cargo.lock

@@ -1034,6 +1034,7 @@ dependencies = [
  "rpassword",
  "serde",
  "serde_json",
+ "sha2",
  "tokio",
 ]
 

Cargo.toml

@@ -21,3 +21,4 @@ dirs        = "5"
 argon2      = "0.5"
 aes-gcm     = "0.10"
 rpassword   = "7"
+sha2        = "0.10"

src/commands/wallet.rs

@@ -1,7 +1,8 @@
 use anyhow::Result;
 use clap::Subcommand;
-use k256::ecdsa::SigningKey;
+use k256::ecdsa::{signature::Signer, Signature, SigningKey};
 use rand::rngs::OsRng;
+use sha2::{Digest, Sha256};
 
 use crate::keystore;
 
@@ -17,7 +18,7 @@ pub enum WalletCmd {
         #[arg(long, default_value = "default")]
         label: String,
     },
-    /// Send NUT tokens (stub — Faz 1 tx signing)
+    /// Send Shell tokens to another address
     Send {
         #[arg(long)] to:     String,
         #[arg(long)] amount: u64,
@@ -57,7 +58,40 @@ pub async fn run(cmd: WalletCmd) -> Result<()> {
         }
 
         WalletCmd::Send { to, amount, from } => {
-            println!("TODO: nu wallet send --to {to} --amount {amount} Shell (from: {from}) — Faz 1");
+            let rpc_url = std::env::var("NU_RPC_URL")
+                .unwrap_or_else(|_| "http://localhost:8545".to_string());
+            let client = crate::rpc::Client::new(&rpc_url);
+
+            let dir       = crate::config::keystore_dir();
+            let path      = dir.join(format!("{from}.key"));
+            let password  = keystore::prompt_password(false)?;
+            let key_bytes = keystore::load_encrypted(&path, &password)?;
+            let key       = SigningKey::from_bytes(key_bytes.as_slice().into())?;
+            let sender    = hex::encode(key.verifying_key().to_sec1_bytes());
+
+            let account   = client.call("nu_getAccount", vec![serde_json::json!(sender)]).await?;
+            let nonce: u64 = account["nonce"].as_u64().unwrap_or(0);
+
+            let payload = serde_json::json!({
+                "TokenTransfer": { "to": to, "amount": amount }
+            });
+            let payload_bytes = serde_json::to_vec(&payload)?;
+            let tx_id = hex::encode(Sha256::digest(&payload_bytes));
+
+            let sig: Signature = key.sign(tx_id.as_bytes());
+            let sig_bytes      = sig.to_bytes().to_vec();
+
+            let tx = serde_json::json!({
+                "tx_id":   tx_id,
+                "sender":  sender,
+                "nonce":   nonce,
+                "fee":     0,
+                "sig":     sig_bytes,
+                "payload": payload,
+            });
+
+            let result = client.call("nu_sendRawTx", vec![tx]).await?;
+            println!("Sent: {}", result["tx_id"].as_str().unwrap_or("?"));
         }
     }
     Ok(())