feat(api-key): add IP whitelist/blacklist restriction and usage log IP tracking

- Add IP restriction feature for API keys (whitelist/blacklist with CIDR support)
- Add IP address logging to usage logs (admin-only visibility)
- Remove billing_type column from usage logs UI (redundant)
- Use generic "Access denied" error message for security

Backend:
- New ip package with IP/CIDR validation and matching utilities
- Database migrations for ip_whitelist, ip_blacklist (api_keys) and ip_address (usage_logs)
- Middleware IP restriction check after API key validation
- Input validation for IP/CIDR patterns on create/update

Frontend:
- API key form with enable toggle for IP restriction
- Shield icon indicator in table for keys with IP restriction
- Removed billing_type filter and column from usage views

backend/internal/handler/dto/mappers.go

@@ -53,16 +53,18 @@ func APIKeyFromService(k *service.APIKey) *APIKey {
 		return nil
 	}
 	return &APIKey{
-		ID:        k.ID,
-		UserID:    k.UserID,
-		Key:       k.Key,
-		Name:      k.Name,
-		GroupID:   k.GroupID,
-		Status:    k.Status,
-		CreatedAt: k.CreatedAt,
-		UpdatedAt: k.UpdatedAt,
-		User:      UserFromServiceShallow(k.User),
-		Group:     GroupFromServiceShallow(k.Group),
+		ID:          k.ID,
+		UserID:      k.UserID,
+		Key:         k.Key,
+		Name:        k.Name,
+		GroupID:     k.GroupID,
+		Status:      k.Status,
+		IPWhitelist: k.IPWhitelist,
+		IPBlacklist: k.IPBlacklist,
+		CreatedAt:   k.CreatedAt,
+		UpdatedAt:   k.UpdatedAt,
+		User:        UserFromServiceShallow(k.User),
+		Group:       GroupFromServiceShallow(k.Group),
 	}
 }
 
@@ -250,11 +252,12 @@ func AccountSummaryFromService(a *service.Account) *AccountSummary {
 
 // usageLogFromServiceBase is a helper that converts service UsageLog to DTO.
 // The account parameter allows caller to control what Account info is included.
-func usageLogFromServiceBase(l *service.UsageLog, account *AccountSummary) *UsageLog {
+// The includeIPAddress parameter controls whether to include the IP address (admin-only).
+func usageLogFromServiceBase(l *service.UsageLog, account *AccountSummary, includeIPAddress bool) *UsageLog {
 	if l == nil {
 		return nil
 	}
-	return &UsageLog{
+	result := &UsageLog{
 		ID:                    l.ID,
 		UserID:                l.UserID,
 		APIKeyID:              l.APIKeyID,
@@ -290,21 +293,26 @@ func usageLogFromServiceBase(l *service.UsageLog, account *AccountSummary) *Usag
 		Group:                 GroupFromServiceShallow(l.Group),
 		Subscription:          UserSubscriptionFromService(l.Subscription),
 	}
+	// IP 地址仅对管理员可见
+	if includeIPAddress {
+		result.IPAddress = l.IPAddress
+	}
+	return result
 }
 
 // UsageLogFromService converts a service UsageLog to DTO for regular users.
-// It excludes Account details - users should not see account information.
+// It excludes Account details and IP address - users should not see these.
 func UsageLogFromService(l *service.UsageLog) *UsageLog {
-	return usageLogFromServiceBase(l, nil)
+	return usageLogFromServiceBase(l, nil, false)
 }
 
 // UsageLogFromServiceAdmin converts a service UsageLog to DTO for admin users.
-// It includes minimal Account info (ID, Name only).
+// It includes minimal Account info (ID, Name only) and IP address.
 func UsageLogFromServiceAdmin(l *service.UsageLog) *UsageLog {
 	if l == nil {
 		return nil
 	}
-	return usageLogFromServiceBase(l, AccountSummaryFromService(l.Account))
+	return usageLogFromServiceBase(l, AccountSummaryFromService(l.Account), true)
 }
 
 func SettingFromService(s *service.Setting) *Setting {

backend/internal/handler/dto/types.go

@@ -20,14 +20,16 @@ type User struct {
 }
 
 type APIKey struct {
-	ID        int64     `json:"id"`
-	UserID    int64     `json:"user_id"`
-	Key       string    `json:"key"`
-	Name      string    `json:"name"`
-	GroupID   *int64    `json:"group_id"`
-	Status    string    `json:"status"`
-	CreatedAt time.Time `json:"created_at"`
-	UpdatedAt time.Time `json:"updated_at"`
+	ID          int64     `json:"id"`
+	UserID      int64     `json:"user_id"`
+	Key         string    `json:"key"`
+	Name        string    `json:"name"`
+	GroupID     *int64    `json:"group_id"`
+	Status      string    `json:"status"`
+	IPWhitelist []string  `json:"ip_whitelist"`
+	IPBlacklist []string  `json:"ip_blacklist"`
+	CreatedAt   time.Time `json:"created_at"`
+	UpdatedAt   time.Time `json:"updated_at"`
 
 	User  *User  `json:"user,omitempty"`
 	Group *Group `json:"group,omitempty"`
@@ -187,6 +189,9 @@ type UsageLog struct {
 	// User-Agent
 	UserAgent *string `json:"user_agent"`
 
+	// IP 地址（仅管理员可见）
+	IPAddress *string `json:"ip_address,omitempty"`
+
 	CreatedAt time.Time `json:"created_at"`
 
 	User         *User             `json:"user,omitempty"`