fix: implement Claude API key save RPC, VPN status on home page

- Add system.settings.get/set RPC methods for Claude API key management
- Save key to secrets/claude-api-key, restart claude-api-proxy service
- Home Network card now fetches VPN status via vpn.status RPC
- Shows provider name (nostr-vpn, tailscale) instead of just "Connected"

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

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

@@ -292,6 +292,8 @@ impl RpcHandler {
             "system.disk-cleanup" => self.handle_system_disk_cleanup().await,
             "system.reboot" => self.handle_system_reboot(params).await,
             "system.factory-reset" => self.handle_system_factory_reset(params).await,
+            "system.settings.get" => self.handle_system_settings_get(params).await,
+            "system.settings.set" => self.handle_system_settings_set(params).await,
 
             // Opt-in anonymous analytics
             "analytics.get-status" => self.handle_analytics_get_status().await,