Sprint 5.1: JSON snake_case tags + lowercased fields

- All response types now use lowercase json tags (id, name, photo_url, etc.)
- email/phone/birthdate/last_seen_at/photo_url use omitempty
- audit.Metadata type []byte (was map[string]any)
- fixes register/login inconsistency where login returned ID/Name (CamelCase)
  while register returned id/name (lowercase)

internal/audit/repo.go

@@ -9,15 +9,15 @@ import (
 )
 
 type Event struct {
-	ID         int64
-	UserID     *uuid.UUID
-	Action     string
-	TargetType string
-	TargetID   string
-	Metadata   map[string]any
-	IP         string
-	UserAgent  string
-	CreatedAt  time.Time
+	ID         int64     `json:"id"`
+	UserID     *uuid.UUID `json:"user_id,omitempty"`
+	Action     string    `json:"action"`
+	TargetType string    `json:"target_type,omitempty"`
+	TargetID   string    `json:"target_id,omitempty"`
+	Metadata   []byte    `json:"metadata,omitempty"`
+	IP         string    `json:"ip,omitempty"`
+	UserAgent  string    `json:"user_agent,omitempty"`
+	CreatedAt  time.Time `json:"created_at"`
 }
 
 type Repo struct {

internal/chat/repo.go

@@ -11,24 +11,24 @@ import (
 )
 
 type Chat struct {
-	ID         uuid.UUID
-	UserA      uuid.UUID
-	UserB      uuid.UUID
-	CreatedAt  time.Time
-	LastMsgAt  time.Time
+	ID        uuid.UUID `json:"id"`
+	UserA     uuid.UUID `json:"user_a"`
+	UserB     uuid.UUID `json:"user_b"`
+	CreatedAt time.Time `json:"created_at"`
+	LastMsgAt time.Time `json:"last_msg_at"`
 }
 
 type Message struct {
-	ID        uuid.UUID
-	ChatID    uuid.UUID
-	SenderID  uuid.UUID
-	Body      string
-	PhotoURL  string
-	Read      bool
-	Edited    bool
-	Deleted   bool
-	CreatedAt time.Time
-	UpdatedAt time.Time
+	ID        uuid.UUID `json:"id"`
+	ChatID    uuid.UUID `json:"chat_id"`
+	SenderID  uuid.UUID `json:"sender_id"`
+	Body      string    `json:"body"`
+	PhotoURL  string    `json:"photo_url,omitempty"`
+	Read      bool      `json:"read"`
+	Edited    bool      `json:"edited"`
+	Deleted   bool      `json:"deleted"`
+	CreatedAt time.Time `json:"created_at"`
+	UpdatedAt time.Time `json:"updated_at"`
 }
 
 type Repo struct {
@@ -87,13 +87,13 @@ func (r *Repo) GetByID(ctx context.Context, id uuid.UUID) (*Chat, error) {
 
 // ListChats — список чатов пользователя с инфой по последнему сообщению
 type ChatListItem struct {
-	Chat          Chat
-	OtherID       uuid.UUID
-	OtherName     string
-	OtherPhoto    string
-	LastMessage   string
-	LastMsgAt     time.Time
-	UnreadCount   int
+	Chat        Chat      `json:"chat"`
+	OtherID     uuid.UUID `json:"other_id"`
+	OtherName   string    `json:"other_name"`
+	OtherPhoto  string    `json:"other_photo,omitempty"`
+	LastMessage string    `json:"last_message"`
+	LastMsgAt   time.Time `json:"last_msg_at"`
+	UnreadCount int       `json:"unread_count"`
 }
 
 func (r *Repo) ListChats(ctx context.Context, me uuid.UUID, limit, offset int) ([]ChatListItem, error) {

internal/locations/repo.go

@@ -11,11 +11,11 @@ import (
 )
 
 type Location struct {
-	UserID    uuid.UUID
-	Lat       float64
-	Lng       float64
-	Visible   bool
-	UpdatedAt time.Time
+	UserID    uuid.UUID `json:"user_id"`
+	Lat       float64   `json:"lat"`
+	Lng       float64   `json:"lng"`
+	Visible   bool      `json:"visible"`
+	UpdatedAt time.Time `json:"updated_at"`
 }
 
 type Repo struct {

internal/preferences/repo.go

@@ -27,12 +27,12 @@ var AllowedPurposes = map[string]bool{
 }
 
 type Prefs struct {
-	UserID     uuid.UUID
-	Drinks     []string
-	Activities []string
-	Purposes   []string
-	Language   string
-	UpdatedAt  time.Time
+	UserID     uuid.UUID `json:"user_id"`
+	Drinks     []string  `json:"drinks"`
+	Activities []string  `json:"activities"`
+	Purposes   []string  `json:"purposes"`
+	Language   string    `json:"language"`
+	UpdatedAt  time.Time `json:"updated_at"`
 }
 
 type Repo struct {

internal/reviews/repo.go

@@ -11,22 +11,22 @@ import (
 )
 
 type Review struct {
-	ID         uuid.UUID
-	ReviewerID uuid.UUID
-	ReviewedID uuid.UUID
-	ChatID     uuid.UUID
-	Rating     int
-	Body       string
-	Anonymous  bool
-	CreatedAt  time.Time
+	ID         uuid.UUID `json:"id"`
+	ReviewerID uuid.UUID `json:"reviewer_id"`
+	ReviewedID uuid.UUID `json:"reviewed_id"`
+	ChatID     uuid.UUID `json:"chat_id"`
+	Rating     int       `json:"rating"`
+	Body       string    `json:"body"`
+	Anonymous  bool      `json:"anonymous"`
+	CreatedAt  time.Time `json:"created_at"`
 }
 
 type Stats struct {
-	UserID       uuid.UUID
-	RatingAvg    float64
-	RatingCount  int
-	ReviewsLeft  int
-	LastActiveAt *time.Time
+	UserID       uuid.UUID  `json:"user_id"`
+	RatingAvg    float64    `json:"rating_avg"`
+	RatingCount  int        `json:"rating_count"`
+	ReviewsLeft  int        `json:"reviews_left"`
+	LastActiveAt *time.Time `json:"last_active_at,omitempty"`
 }
 
 type Repo struct {

internal/users/repo.go

@@ -11,20 +11,20 @@ import (
 )
 
 type User struct {
-	ID           uuid.UUID
-	Email        string
-	Phone        string
-	Name         string
-	Birthdate    *time.Time
-	Gender       string
-	City         string
-	Bio          string
-	PhotoURL     string
-	IsVerified   bool
-	IsBlocked    bool
-	CreatedAt    time.Time
-	UpdatedAt    time.Time
-	LastSeenAt   *time.Time
+	ID          uuid.UUID  `json:"id"`
+	Email       string     `json:"email,omitempty"`
+	Phone       string     `json:"phone,omitempty"`
+	Name        string     `json:"name"`
+	Birthdate   *time.Time `json:"birthdate,omitempty"`
+	Gender      string     `json:"gender"`
+	City        string     `json:"city"`
+	Bio         string     `json:"bio"`
+	PhotoURL    string     `json:"photo_url,omitempty"`
+	IsVerified  bool       `json:"is_verified"`
+	IsBlocked   bool       `json:"is_blocked"`
+	CreatedAt   time.Time  `json:"created_at"`
+	UpdatedAt   time.Time  `json:"updated_at"`
+	LastSeenAt  *time.Time `json:"last_seen_at,omitempty"`
 }
 
 type Repo struct {