test: US-08 DWN sync tests pass 50/50 — fix sync performance

- Make dwn.sync endpoint async: spawns background task, returns immediately
- Add 90s overall timeout to sync_with_peers via tokio::time::timeout
- Deduplicate peer onion addresses before syncing
- Batch message pushes (50 per request) instead of one-at-a-time over Tor
- Add 15s connect_timeout to Tor SOCKS5 client
- Cap local message query to 200 messages per sync
- Fix DWN HTTP handler to process ALL messages in batch (was only first)
- Add recordId deduplication in handler to prevent duplicate imports
- Update test script to poll dwn.status for sync completion

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

core/archipelago/src/api/rpc/dwn.rs

@@ -31,7 +31,18 @@ impl RpcHandler {
     }
 
     /// Trigger DWN sync with connected peers.
+    /// Spawns sync as a background task and returns immediately.
     pub(super) async fn handle_dwn_sync(&self) -> Result<serde_json::Value> {
+        // Check if already syncing
+        let current_state = dwn_sync::load_sync_state(&self.config.data_dir).await?;
+        if matches!(current_state.status, dwn_sync::SyncStatus::Syncing) {
+            return Ok(serde_json::json!({
+                "sync_status": "syncing",
+                "last_sync": current_state.last_sync,
+                "messages_synced": current_state.messages_synced,
+            }));
+        }
+
         let nodes = federation::load_nodes(&self.config.data_dir).await?;
         let onions: Vec<String> = nodes
             .iter()
@@ -39,12 +50,19 @@ impl RpcHandler {
             .map(|n| n.onion.clone())
             .collect();
 
-        let state = dwn_sync::sync_with_peers(&self.config.data_dir, &onions).await?;
+        // Spawn sync in background so we don't block the RPC response
+        let data_dir = self.config.data_dir.clone();
+        tokio::spawn(async move {
+            if let Err(e) = dwn_sync::sync_with_peers(&data_dir, &onions).await {
+                tracing::warn!(error = %e, "DWN background sync failed");
+            }
+        });
 
+        // Return immediately with "syncing" status
         Ok(serde_json::json!({
-            "sync_status": state.status,
-            "last_sync": state.last_sync,
-            "messages_synced": state.messages_synced,
+            "sync_status": "syncing",
+            "last_sync": current_state.last_sync,
+            "messages_synced": current_state.messages_synced,
         }))
     }