fix: use correct mainline v2 API for DHT operations

- get_mutable takes &[u8; 32] directly (not VerifyingKey)
- MutableItem::new takes bytes::Bytes (not Vec<u8>)
- Remove VerifyingKey import (not exported from mainline v2)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

core/archipelago/src/network/did_dht.rs

@@ -108,7 +108,7 @@ pub async fn create_and_publish(
     let dht = mainline::Dht::client().context("Failed to create DHT client")?;
 
     let signer = mainline::SigningKey::from_bytes(&signing_key.to_bytes());
-    let item = mainline::MutableItem::new(signer, payload, 0, None);
+    let item = mainline::MutableItem::new(signer, bytes::Bytes::from(payload), 0, None);
 
     dht.put_mutable(item).context("Failed to publish to DHT")?;
 
@@ -127,17 +127,13 @@ pub async fn resolve(did: &str, cache: Option<&DhtDidCache>) -> Result<serde_jso
     }
 
     let pubkey_bytes = pubkey_from_did(did)?;
-    let verifying_key = mainline::VerifyingKey::from_bytes(&pubkey_bytes)
-        .map_err(|e| anyhow::anyhow!("Invalid Ed25519 key: {:?}", e))?;
-    let target = mainline::MutableItem::target_from_key(&verifying_key, &None);
 
     let dht = mainline::Dht::client().context("Failed to create DHT client")?;
 
     let response = tokio::time::timeout(
         std::time::Duration::from_secs(30),
         tokio::task::spawn_blocking(move || {
-            // get_mutable returns a Result<IntoIter<MutableItem>>
-            match dht.get_mutable(&target, None, None) {
+            match dht.get_mutable(&pubkey_bytes, None, None) {
                 Ok(mut iter) => iter.next(),
                 Err(_) => None,
             }