Fix R128 and remaining ID fields to accept both JSON types

- Track.R128 and TrackShort.R128: float64 → JSONR128 (accepts both JSON number and object)
- All remaining primary ID fields: string → JSONID (accepts both JSON string and number)
  Fixed in: account, artist, clip, concert, feed, label, landing, metatag,
  music_history, pin, queue, radio, search, settings, supplement

internal/models/base.go

@@ -110,3 +110,34 @@ func (id *JSONID) UnmarshalJSON(data []byte) error {
 func (id JSONID) String() string {
 	return string(id)
 }
+
+// JSONR128 is a flexible R128 loudness normalization value that accepts both JSON numbers and objects.
+// The Yandex Music API sometimes returns r128 as a number (e.g., -23.5) and sometimes
+// as an object (e.g., {"value": -23.5}). JSONR128 accepts both and stores as float64.
+type JSONR128 float64
+
+// UnmarshalJSON implements json.Unmarshaler, accepting both JSON numbers and objects.
+func (r *JSONR128) UnmarshalJSON(data []byte) error {
+	// Try float64 first
+	var f float64
+	if err := json.Unmarshal(data, &f); err == nil {
+		*r = JSONR128(f)
+		return nil
+	}
+	// Try object with "value" key
+	var obj struct {
+		Value float64 `json:"value"`
+	}
+	if err := json.Unmarshal(data, &obj); err == nil {
+		*r = JSONR128(obj.Value)
+		return nil
+	}
+	// Default to 0 if neither format works
+	*r = 0
+	return nil
+}
+
+// Float64 returns the R128 value as a float64.
+func (r JSONR128) Float64() float64 {
+	return float64(r)
+}