feat!: probes link to the panel; signed release updates for container nodes [CI]

Probes connect to the panel directly and get the agent list as desired state.
CI signs the image digest of agent and probe releases, the panel forwards the
manifest, and a host updater verifies it with a local public key, pulls by
digest and rolls back when the new version is unhealthy.

backend/src/Monitor.Backend.Gateway/GatewayServiceCollectionExtensions.cs

@@ -20,6 +20,7 @@ public static class GatewayServiceCollectionExtensions
         services.AddFleetEnrollment();
         services.AddFleetServer(options => options.NodeIdPrefix = AgentIds.Prefix)
             .AddState<TaskSetStateProvider>()
+            .AddState<ProbeAgentsStateProvider>()
             .AddInbox<RawChunkInbox>()
             .MapMethods(MapMonitorMethods);
         return services;
@@ -39,11 +40,6 @@ public static class GatewayServiceCollectionExtensions
             .OnNotify(
                 MonitorMethods.TestStatus,
                 MonitorJsonContext.Default.TestStatusParams,
-                (context, parameters, ct) => services.GetRequiredService<TestService>().OnStatusAsync(context.Node.Id, parameters, ct))
-            .On(
-                MonitorMethods.ProbeAgents,
-                MonitorJsonContext.Default.ProbeAgentsParams,
-                MonitorJsonContext.Default.ProbeAgentsResult,
-                async (context, parameters, ct) => Result<ProbeAgentsResult>.Ok(await services.GetRequiredService<AgentService>().ProbeAgentsAsync(ct)));
+                (context, parameters, ct) => services.GetRequiredService<TestService>().OnStatusAsync(context.Node.Id, parameters, ct));
     }
 }