Add per-node health checks with status indicators and scheduled probes.

service/internal/settings/types.go

@@ -105,6 +105,14 @@ type Node struct {
 	PublicKey string    `json:"public_key"`
 	KeyAlgo   string    `json:"key_algo"`
 	CreatedAt time.Time `json:"created_at"`
+
+	// Health check configuration and last result (persisted).
+	HealthCheckIntervalSeconds int        `json:"health_check_interval_seconds"`
+	HealthLastCheckedAt        *time.Time `json:"health_last_checked_at,omitempty"`
+	HealthPingOK               *bool      `json:"health_ping_ok,omitempty"`
+	HealthSSHOK                *bool      `json:"health_ssh_ok,omitempty"`
+	HealthOK                   *bool      `json:"health_ok,omitempty"`
+	HealthMessage              string     `json:"health_message,omitempty"`
 }
 
 // NodeStore is the plain JSON payload in nodes.json.
@@ -284,10 +292,11 @@ type NodeKeyStore struct {
 type NodeAuditAction string
 
 const (
-	NodeAuditActionCreate  NodeAuditAction = "create"
-	NodeAuditActionDelete  NodeAuditAction = "delete"
-	NodeAuditActionTestSSH NodeAuditAction = "test_ssh"
-	NodeAuditActionUpdate  NodeAuditAction = "update"
+	NodeAuditActionCreate      NodeAuditAction = "create"
+	NodeAuditActionDelete      NodeAuditAction = "delete"
+	NodeAuditActionTestSSH     NodeAuditAction = "test_ssh"
+	NodeAuditActionHealthCheck NodeAuditAction = "health_check"
+	NodeAuditActionUpdate      NodeAuditAction = "update"
 )
 
 // NodeAuditEvent is one append-only record of a node mutation.