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.Api/Common/Mappers.cs

@@ -40,7 +40,7 @@ public static class Mappers
 
     public static ProbeDto ToDto(ProbeView v) =>
         new(
-            v.Probe.Id, v.Probe.Name, Time(v.Probe.CreatedAtMs), Time(v.Probe.RevokedAtMs), v.Revoked,
+            v.Probe.Id, v.Probe.Name, Time(v.Probe.CreatedAtMs), Time(v.Probe.RevokedAtMs), v.Revoked, v.Online,
             [.. v.Connections.Select(c => new ProbeConnectionDto(c.AgentId.Value, c.AgentName, c.AgentOnline, c.Version, c.Remote, Time(c.SinceMs)))]);
 
     public static SeriesDto ToDto(SeriesResult r, bool live) =>