Add comprehensive godoc documentation to all exported symbols

- Document all exported types, functions, methods, and constants across 52 files
- Add package-level doc comments to client, models, utils, and ynison packages
- Document HTTP method and endpoint path for each API client method
- Document model struct fields and DeJSON/DeList/ToJSON/ToMap methods
- Fix duplicate package doc comment in internal/models/base.go

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

internal/client/concerts.go

@@ -1,3 +1,4 @@
+// Package client provides methods for interacting with Yandex Music API endpoints.
 package client
 
 import (
@@ -7,7 +8,7 @@ import (
 	"gitea.mrixs.me/Mrixs/yandex-music-api-go/internal/models"
 )
 
-// GetConcerts gets concerts
+// GetConcerts gets concerts with pagination (GET /concerts).
 func (c *Client) GetConcerts(ctx context.Context, page, pageSize int) (*models.ConcertFeed, error) {
 	params := map[string]string{
 		"page":      "1",
@@ -27,7 +28,7 @@ func (c *Client) GetConcerts(ctx context.Context, page, pageSize int) (*models.C
 	return &result, nil
 }
 
-// GetConcertFeed gets concert feed
+// GetConcertFeed gets the concert feed (GET /concerts/feed).
 func (c *Client) GetConcertFeed(ctx context.Context) (*models.ConcertFeed, error) {
 	var result models.ConcertFeed
 	if err := c.request.Get(ctx, "/concerts/feed", nil, &result); err != nil {
@@ -36,8 +37,7 @@ func (c *Client) GetConcertFeed(ctx context.Context) (*models.ConcertFeed, error
 	return &result, nil
 }
 
-// GetConcertInfo gets concert info
-// GET /concerts/{concertID}/info
+// GetConcertInfo gets concert info by ID (GET /concerts/{concertID}/info).
 func (c *Client) GetConcertInfo(ctx context.Context, concertID string) (*models.ConcertInfo, error) {
 	var result models.ConcertInfo
 	if err := c.request.Get(ctx, fmt.Sprintf("/concerts/%s/info", concertID), nil, &result); err != nil {
@@ -46,7 +46,7 @@ func (c *Client) GetConcertInfo(ctx context.Context, concertID string) (*models.
 	return &result, nil
 }
 
-// GetConcertLocations gets concert locations
+// GetConcertLocations gets concert locations (GET /concerts/locations).
 func (c *Client) GetConcertLocations(ctx context.Context) (*models.ConcertLocations, error) {
 	var result models.ConcertLocations
 	if err := c.request.Get(ctx, "/concerts/locations", nil, &result); err != nil {
@@ -55,8 +55,7 @@ func (c *Client) GetConcertLocations(ctx context.Context) (*models.ConcertLocati
 	return &result, nil
 }
 
-// GetConcertTabs gets concert tabs
-// GET /concerts/tab-config
+// GetConcertTabs gets concert tab configuration (GET /concerts/tab-config).
 func (c *Client) GetConcertTabs(ctx context.Context) (*models.ConcertTabConfig, error) {
 	var result models.ConcertTabConfig
 	if err := c.request.Get(ctx, "/concerts/tab-config", nil, &result); err != nil {