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/models/artist.go

@@ -1,10 +1,11 @@
+// Package models provides data models for the Yandex Music API.
 package models
 
 import (
 	"encoding/json"
 )
 
-// Artist represents a full artist
+// Artist represents a full artist from the Yandex Music API.
 type Artist struct {
 	BaseModel
 	ID          string       `json:"id"`
@@ -34,7 +35,7 @@ type Artist struct {
 	TracksData []Track          `json:"tracks_data"`
 }
 
-// DeJSON deserializes an Artist from JSON
+// DeJSON deserializes an Artist from JSON data.
 func (a *Artist) DeJSON(data []byte, c ClientInterface) (Model, error) {
 	var raw map[string]json.RawMessage
 	if err := json.Unmarshal(data, &raw); err != nil {
@@ -146,7 +147,7 @@ func (a *Artist) DeJSON(data []byte, c ClientInterface) (Model, error) {
 	return artist, nil
 }
 
-// DeList deserializes a list of Artists
+// DeList deserializes a list of Artists from JSON data.
 func (a *Artist) DeList(data []byte, c ClientInterface) ([]Model, error) {
 	var rawList []json.RawMessage
 	if err := json.Unmarshal(data, &rawList); err != nil {
@@ -164,27 +165,27 @@ func (a *Artist) DeList(data []byte, c ClientInterface) ([]Model, error) {
 	return result, nil
 }
 
-// Ratings represents artist ratings
+// Ratings represents artist ratings.
 type Ratings struct {
 	Rating float64 `json:"rating"`
 	Votes  int     `json:"votes"`
 }
 
-// Counts represents artist counts
+// Counts represents artist counts.
 type Counts struct {
 	Tracks  int `json:"tracks"`
 	Albums  int `json:"albums"`
 	Folders int `json:"folders"`
 }
 
-// SocialLink represents a social media link
+// SocialLink represents a social media link.
 type SocialLink struct {
 	URL   string `json:"url"`
 	Title string `json:"title"`
 	Type  string `json:"type"`
 }
 
-// Cover represents cover image info
+// Cover represents cover image info.
 type Cover struct {
 	URI        string `json:"uri"`
 	Type       string `json:"type"`
@@ -193,13 +194,13 @@ type Cover struct {
 	Background string `json:"background"`
 }
 
-// ArtistBriefInfo represents brief artist info
+// ArtistBriefInfo represents brief artist info.
 type ArtistBriefInfo struct {
 	Description string `json:"description"`
 	Available   bool   `json:"available"`
 }
 
-// ArtistDonations represents artist donations info
+// ArtistDonations represents artist donations info.
 type ArtistDonations struct {
 	Items  []DonationItem `json:"items"`
 	Total  int            `json:"total"`
@@ -207,7 +208,7 @@ type ArtistDonations struct {
 	Raised int            `json:"raised"`
 }
 
-// DonationItem represents a donation item
+// DonationItem represents a donation item.
 type DonationItem struct {
 	ID          string `json:"id"`
 	Title       string `json:"title"`
@@ -218,7 +219,7 @@ type DonationItem struct {
 	Currency    string `json:"currency"`
 }
 
-// ConcertShort represents a concert (minimal for artist)
+// ConcertShort represents a concert (minimal for artist).
 type ConcertShort struct {
 	BaseModel
 	ID        string `json:"id"`
@@ -233,7 +234,7 @@ type ConcertShort struct {
 	Available bool   `json:"available"`
 }
 
-// DeJSON deserializes a ConcertShort from JSON
+// DeJSON deserializes a ConcertShort from JSON data.
 func (c *ConcertShort) DeJSON(data []byte, client ClientInterface) (Model, error) {
 	var raw map[string]json.RawMessage
 	if err := json.Unmarshal(data, &raw); err != nil {
@@ -276,7 +277,7 @@ func (c *ConcertShort) DeJSON(data []byte, client ClientInterface) (Model, error
 	return concert, nil
 }
 
-// DeList deserializes a list of ConcertShort
+// DeList deserializes a list of ConcertShort from JSON data.
 func (c *ConcertShort) DeList(data []byte, client ClientInterface) ([]Model, error) {
 	var rawList []json.RawMessage
 	if err := json.Unmarshal(data, &rawList); err != nil {
@@ -294,7 +295,7 @@ func (c *ConcertShort) DeList(data []byte, client ClientInterface) ([]Model, err
 	return result, nil
 }
 
-// ClipShort represents a clip (minimal for artist)
+// ClipShort represents a clip (minimal for artist).
 type ClipShort struct {
 	BaseModel
 	ID         string `json:"id"`
@@ -308,7 +309,7 @@ type ClipShort struct {
 	CreatedAt  string `json:"created_at"`
 }
 
-// DeJSON deserializes a ClipShort from JSON
+// DeJSON deserializes a ClipShort from JSON data.
 func (c *ClipShort) DeJSON(data []byte, client ClientInterface) (Model, error) {
 	var raw map[string]json.RawMessage
 	if err := json.Unmarshal(data, &raw); err != nil {
@@ -348,7 +349,7 @@ func (c *ClipShort) DeJSON(data []byte, client ClientInterface) (Model, error) {
 	return clip, nil
 }
 
-// DeList deserializes a list of ClipShort
+// DeList deserializes a list of ClipShort from JSON data.
 func (c *ClipShort) DeList(data []byte, client ClientInterface) ([]Model, error) {
 	var rawList []json.RawMessage
 	if err := json.Unmarshal(data, &rawList); err != nil {