feat: add opt-in anonymous node analytics (Y4-03)

New RPC endpoints:
- analytics.get-status: Check if analytics opted in
- analytics.enable/disable: Toggle opt-in
- analytics.get-snapshot: Anonymous aggregate data (version, app count,
  hardware tier, CPU cores, RAM, federation peers)

No personal data: no DIDs, no IPs, no secrets. Strictly opt-in.

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

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

@@ -1,3 +1,4 @@
+mod analytics;
 mod auth;
 mod backup_rpc;
 mod bitcoin;
@@ -577,6 +578,12 @@ impl RpcHandler {
             "system.disk-status" => self.handle_system_disk_status().await,
             "system.disk-cleanup" => self.handle_system_disk_cleanup().await,
 
+            // Opt-in anonymous analytics
+            "analytics.get-status" => self.handle_analytics_get_status().await,
+            "analytics.enable" => self.handle_analytics_enable().await,
+            "analytics.disable" => self.handle_analytics_disable().await,
+            "analytics.get-snapshot" => self.handle_analytics_get_snapshot().await,
+
             // Real-time metrics monitoring
             "monitoring.current" => self.handle_monitoring_current().await,
             "monitoring.history" => self.handle_monitoring_history(params).await,