Fix ID fields to accept both JSON strings and numbers

The Yandex Music API returns IDs as both JSON strings and numbers depending
on the endpoint. Added JSONID custom type in internal/models/base.go that
implements json.Unmarshaler to accept both formats and store as string.

Changed ID fields from string to JSONID:
- Track.ID, Major.ID, TrackLyricsInfo.ID (track.go)
- Album.ID, TrailerInfo.TrackID, TrailerInfo.AlbumID (album.go)

Updated example to convert JSONID to string when passing to client methods.

Co-Authored-By: Claude Code <noreply@anthropic.com>

internal/models/album.go

@@ -8,20 +8,20 @@ import (
 // Album represents a full album from the Yandex Music API.
 type Album struct {
 	BaseModel
-	ID          string     `json:"id"`
-	Title       string     `json:"title"`
-	CoverURI    string     `json:"cover_uri"`
-	Genre       string     `json:"genre"`
-	Year        int        `json:"year"`
-	TrackCount  int        `json:"track_count"`
-	Available   bool       `json:"available"`
-	ReleaseDate string     `json:"release_date"`
-	Artists     []Artist   `json:"artists"`
-	Labels      []Label    `json:"labels"`
-	Volumes     [][]Track  `json:"volumes"`
-	Description string     `json:"description"`
-	Meta        *AlbumMeta `json:"meta"`
-	Best        *Best      `json:"best"`
+	ID          JSONID      `json:"id"`
+	Title       string      `json:"title"`
+	CoverURI    string      `json:"cover_uri"`
+	Genre       string      `json:"genre"`
+	Year        int         `json:"year"`
+	TrackCount  int         `json:"track_count"`
+	Available   bool        `json:"available"`
+	ReleaseDate string      `json:"release_date"`
+	Artists     []Artist    `json:"artists"`
+	Labels      []Label     `json:"labels"`
+	Volumes     [][]Track   `json:"volumes"`
+	Description string      `json:"description"`
+	Meta        *AlbumMeta  `json:"meta"`
+	Best        *Best       `json:"best"`
 	// Additional fields
 	Region                       string          `json:"region"`
 	AvailableForPremiumUsers     bool            `json:"available_for_premium_users"`
@@ -226,8 +226,8 @@ type Best struct {
 type TrailerInfo struct {
 	BaseModel
 	PreviewURI string `json:"preview_uri"`
-	TrackID    string `json:"track_id"`
-	AlbumID    string `json:"album_id"`
+	TrackID    JSONID `json:"track_id"`
+	AlbumID    JSONID `json:"album_id"`
 	Duration   int    `json:"duration"`
 }