core/server: add generic dbus service

- Add QML client with subscribe/introspect/getprop/setprop/call
- Add CLI helper `dms notify` that allows async calls with action
  handlers.

core/pkg/dbusutil/variant.go

@@ -0,0 +1,69 @@
+package dbusutil
+
+import "github.com/godbus/dbus/v5"
+
+func As[T any](v dbus.Variant) (T, bool) {
+	val, ok := v.Value().(T)
+	return val, ok
+}
+
+func AsOr[T any](v dbus.Variant, def T) T {
+	if val, ok := v.Value().(T); ok {
+		return val
+	}
+	return def
+}
+
+func Get[T any](m map[string]dbus.Variant, key string) (T, bool) {
+	v, ok := m[key]
+	if !ok {
+		var zero T
+		return zero, false
+	}
+	return As[T](v)
+}
+
+func GetOr[T any](m map[string]dbus.Variant, key string, def T) T {
+	v, ok := m[key]
+	if !ok {
+		return def
+	}
+	return AsOr(v, def)
+}
+
+func Normalize(v any) any {
+	switch val := v.(type) {
+	case dbus.Variant:
+		return Normalize(val.Value())
+	case dbus.ObjectPath:
+		return string(val)
+	case []dbus.ObjectPath:
+		result := make([]string, len(val))
+		for i, p := range val {
+			result[i] = string(p)
+		}
+		return result
+	case map[string]dbus.Variant:
+		result := make(map[string]any)
+		for k, vv := range val {
+			result[k] = Normalize(vv.Value())
+		}
+		return result
+	case []any:
+		result := make([]any, len(val))
+		for i, item := range val {
+			result[i] = Normalize(item)
+		}
+		return result
+	default:
+		return v
+	}
+}
+
+func NormalizeSlice(values []any) []any {
+	result := make([]any, len(values))
+	for i, v := range values {
+		result[i] = Normalize(v)
+	}
+	return result
+}