Add per-node action groups with schedules, runs, and logs.

Let operators manage ordered action groups on each host, run them manually or on a schedule over SSH, and inspect disk-backed JSON run logs from a node detail UI.

service/internal/auth/placeholders_test.go

@@ -0,0 +1,18 @@
+package auth
+
+import "testing"
+
+func TestExpandPlaceholders(t *testing.T) {
+	body := "ping {{node.ip}} as {{node.username}} host={{cc.host}} env={{env.FOO}} secret={{secret.TOKEN}} unknown={{nope}}"
+	got := ExpandPlaceholders(body, PlaceholderContext{
+		Host:     "web-1",
+		IP:       "10.0.0.5",
+		Username: "deploy",
+		Env:      map[string]string{"FOO": "bar"},
+		Secrets:  map[string]string{},
+	})
+	want := "ping 10.0.0.5 as deploy host=web-1 env=bar secret= unknown="
+	if got != want {
+		t.Fatalf("got %q want %q", got, want)
+	}
+}