feat: DID persistence + federation node names in sync

Part 1 — DID Persistence:
- Deploy script creates /var/lib/archipelago/identity/ directory
- First-boot script creates identity dir with proper ownership
- Identity load now logs pubkey to confirm persistence across restarts

Part 2 — Node Names:
- NodeStateSnapshot includes node_name field
- build_local_state() passes server name to sync responses
- update_node_state() stores peer's announced name on the FederatedNode
- Names propagate automatically during federation.sync-state

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

scripts/first-boot-containers.sh

@@ -798,11 +798,13 @@ SJSON
   log "Created initial tor-config/services.json"
 fi
 
-# identities: backend identity manager stores DIDs here
+# identity: node Ed25519 keypair (DID) — MUST persist across deployments
+mkdir -p /var/lib/archipelago/identity
+# identities: backend identity manager stores user DIDs here
 mkdir -p /var/lib/archipelago/identities
 
 # Ensure archipelago user can write to these directories
-chown -R 1000:1000 /var/lib/archipelago/tor-config /var/lib/archipelago/identities 2>/dev/null || true
+chown -R 1000:1000 /var/lib/archipelago/tor-config /var/lib/archipelago/identity /var/lib/archipelago/identities 2>/dev/null || true
 
 # 11. Post-boot validation
 log "Validating container creation..."