feat(mesh): show federated Archipelago nodes on the Mesh Map

Peers that opt in via a new "Share Location" toggle in Settings
(server.set-location RPC) get plotted on other trusted peers' Mesh Map
with a distinct Archy-logo marker, separate from raw LoRa radio peers.
Location is persisted locally, carried in NodeStateSnapshot, and
propagated through federation sync/delta like other node state.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

core/archipelago/src/federation/storage.rs

@@ -506,6 +506,8 @@ mod tests {
             nostr_npub: None,
             own_fips_npub: None,
             federated_peers: Vec::new(),
+            lat: None,
+            lon: None,
         };
 
         update_node_state(dir.path(), "did:key:z1", state)