feat: complete Phase 2 transport layer — off-grid mode, transport icons, federation sync

- Add off-grid (mesh only) toggle to Mesh.vue with orange OFF-GRID banner
- Add per-peer transport indicator in Federation.vue (mesh/lan/tor icons)
- Add sync_with_peer_via_transport() for CBOR delta sync via transport router
- Fetch transport store on mount in both Mesh and Federation views

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

core/archipelago/src/federation.rs

@@ -428,6 +428,54 @@ pub async fn sync_with_peer(
     Ok(state)
 }
 
+/// Sync with a peer using the transport router (Mesh > LAN > Tor).
+/// Uses CBOR delta encoding for compact payloads over constrained links.
+/// Falls back to `sync_with_peer()` if no transport router is available.
+pub async fn sync_with_peer_via_transport(
+    data_dir: &Path,
+    peer: &FederatedNode,
+    local_did: &str,
+    previous_state: Option<&NodeStateSnapshot>,
+    router: &crate::transport::TransportRouter,
+) -> Result<()> {
+    use crate::transport::{MessageType, TransportMessage};
+    use crate::transport::delta;
+
+    // Build the sync request payload — if we have a previous state from this peer,
+    // send a delta request (tells the peer we only need changes since timestamp).
+    let payload = if let Some(prev) = previous_state {
+        // Request delta since our last known state
+        let request = serde_json::json!({
+            "type": "state_sync_request",
+            "since": prev.timestamp,
+        });
+        delta::encode_cbor(&delta::StateDelta {
+            ts: prev.timestamp.clone(),
+            v: 1,
+            ..Default::default()
+        })?
+    } else {
+        // First sync — request full state
+        let request = serde_json::json!({ "type": "state_sync_request" });
+        serde_json::to_vec(&request)?
+    };
+
+    let message = TransportMessage {
+        from_did: local_did.to_string(),
+        payload,
+        message_type: MessageType::StateSync,
+    };
+
+    let transport_used = router.send_to_peer(&peer.did, &message).await?;
+    tracing::info!(
+        peer = %peer.did,
+        transport = %transport_used,
+        "Federation sync sent via transport"
+    );
+
+    Ok(())
+}
+
 /// Build the local node's state snapshot for sharing with peers.
 pub fn build_local_state(
     apps: Vec<AppStatus>,