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/concert.go

@@ -1,10 +1,11 @@
+// Package models provides data models for the Yandex Music API.
 package models
 
 import (
 	"encoding/json"
 )
 
-// Concert represents a concert
+// Concert represents a concert from the Yandex Music API.
 type Concert struct {
 	BaseModel
 	ID          string             `json:"id"`
@@ -28,7 +29,7 @@ type Concert struct {
 	Skeleton    *ConcertSkeleton   `json:"skeleton"`
 }
 
-// DeJSON deserializes a Concert from JSON
+// DeJSON deserializes a Concert from JSON data.
 func (c *Concert) DeJSON(data []byte, client ClientInterface) (Model, error) {
 	var raw map[string]json.RawMessage
 	if err := json.Unmarshal(data, &raw); err != nil {
@@ -111,7 +112,7 @@ func (c *Concert) DeJSON(data []byte, client ClientInterface) (Model, error) {
 	return concert, nil
 }
 
-// DeList deserializes a list of Concerts
+// DeList deserializes a list of Concerts from JSON data.
 func (c *Concert) DeList(data []byte, client ClientInterface) ([]Model, error) {
 	var rawList []json.RawMessage
 	if err := json.Unmarshal(data, &rawList); err != nil {
@@ -129,7 +130,7 @@ func (c *Concert) DeList(data []byte, client ClientInterface) ([]Model, error) {
 	return result, nil
 }
 
-// ConcertVenue represents a concert venue
+// ConcertVenue represents a concert venue.
 type ConcertVenue struct {
 	BaseModel
 	ID       string `json:"id"`
@@ -141,7 +142,7 @@ type ConcertVenue struct {
 	ImageURI string `json:"image_uri"`
 }
 
-// ConcertLocation represents a concert location
+// ConcertLocation represents a concert location.
 type ConcertLocation struct {
 	BaseModel
 	ID       string         `json:"id"`
@@ -152,7 +153,7 @@ type ConcertLocation struct {
 	Venues   []ConcertVenue `json:"venues"`
 }
 
-// ConcertLocations represents concert locations
+// ConcertLocations represents concert locations.
 type ConcertLocations struct {
 	BaseModel
 	Locations []ConcertLocation `json:"locations"`
@@ -161,7 +162,7 @@ type ConcertLocations struct {
 	PageSize  int               `json:"page_size"`
 }
 
-// ConcertFeed represents a concert feed
+// ConcertFeed represents a concert feed.
 type ConcertFeed struct {
 	BaseModel
 	Concerts []Concert `json:"concerts"`
@@ -170,14 +171,14 @@ type ConcertFeed struct {
 	PageSize int       `json:"page_size"`
 }
 
-// ConcertInfo represents concert info
+// ConcertInfo represents concert info.
 type ConcertInfo struct {
 	BaseModel
 	Concert *Concert  `json:"concert"`
 	Related []Concert `json:"related"`
 }
 
-// ConcertEventInfo represents concert event info
+// ConcertEventInfo represents concert event info.
 type ConcertEventInfo struct {
 	BaseModel
 	EventID   string          `json:"event_id"`
@@ -186,7 +187,7 @@ type ConcertEventInfo struct {
 	Data      json.RawMessage `json:"data"`
 }
 
-// ConcertDescription represents concert description
+// ConcertDescription represents concert description.
 type ConcertDescription struct {
 	BaseModel
 	Text      string `json:"text"`
@@ -194,7 +195,7 @@ type ConcertDescription struct {
 	ShortText string `json:"short_text"`
 }
 
-// ConcertCashback represents concert cashback
+// ConcertCashback represents concert cashback.
 type ConcertCashback struct {
 	BaseModel
 	Amount   int    `json:"amount"`
@@ -203,14 +204,14 @@ type ConcertCashback struct {
 	Expires  string `json:"expires"`
 }
 
-// ConcertMinPrice represents concert min price
+// ConcertMinPrice represents concert min price.
 type ConcertMinPrice struct {
 	BaseModel
 	Price    int    `json:"price"`
 	Currency string `json:"currency"`
 }
 
-// ConcertTabConfig represents concert tab config
+// ConcertTabConfig represents concert tab config.
 type ConcertTabConfig struct {
 	BaseModel
 	ID     string           `json:"id"`
@@ -220,20 +221,20 @@ type ConcertTabConfig struct {
 	Range  *ConcertTabRange `json:"range"`
 }
 
-// ConcertTabRange represents concert tab range
+// ConcertTabRange represents concert tab range.
 type ConcertTabRange struct {
 	BaseModel
 	From string `json:"from"`
 	To   string `json:"to"`
 }
 
-// ConcertSkeleton represents concert skeleton
+// ConcertSkeleton represents concert skeleton.
 type ConcertSkeleton struct {
 	BaseModel
 	Blocks []ConcertSkeletonBlock `json:"blocks"`
 }
 
-// ConcertSkeletonBlock represents a concert skeleton block
+// ConcertSkeletonBlock represents a concert skeleton block.
 type ConcertSkeletonBlock struct {
 	BaseModel
 	ID    string          `json:"id"`