feat(gateway): add web search emulation for Anthropic API Key accounts

Inject web search capability for Claude Console (API Key) accounts that
don't natively support Anthropic's web_search tool. When a pure
web_search request is detected, the gateway calls Brave Search or Tavily
API directly and constructs an Anthropic-protocol-compliant SSE/JSON
response without forwarding to upstream.

Backend:
- New `pkg/websearch/` SDK: Brave and Tavily provider implementations
  with io.LimitReader, proxy support, and Redis-based quota tracking
  (Lua atomic INCR + TTL, DECR rollback on failure)
- Global config via `settings.web_search_emulation_config` (JSON) with
  in-process cache + singleflight, input validation, API key merge on
  save, and sanitized API responses
- Channel-level toggle via `channels.features_config` JSONB column
  (DB migration 101)
- Account-level toggle via `accounts.extra.web_search_emulation`
- Request interception in `Forward()` with SSE streaming response
  construction using json.Marshal (no manual string concatenation)
- Manager hot-reload: `RebuildWebSearchManager()` called on config save
  and startup via `SetWebSearchRedisClient()`
- 70 unit tests covering providers, manager, config validation,
  sanitization, tool detection, query extraction, and response building

Frontend:
- Settings → Gateway tab: Web Search Emulation config card with global
  toggle, provider list (add/remove, API key, priority, quota, proxy)
- Channels → Anthropic tab: web search emulation toggle with global
  state linkage (disabled when global off)
- Account Create/Edit modals: web search emulation toggle for API Key
  type with Toggle component
- Full i18n coverage (zh + en)

backend/internal/repository/channel_repo.go

@@ -41,10 +41,14 @@ func (r *channelRepository) Create(ctx context.Context, channel *service.Channel
 		if err != nil {
 			return err
 		}
+		featuresConfigJSON, err := marshalFeaturesConfig(channel.FeaturesConfig)
+		if err != nil {
+			return err
+		}
 		err = tx.QueryRowContext(ctx,
-			`INSERT INTO channels (name, description, status, model_mapping, billing_model_source, restrict_models, features) VALUES ($1, $2, $3, $4, $5, $6, $7)
+			`INSERT INTO channels (name, description, status, model_mapping, billing_model_source, restrict_models, features, features_config) VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
 			 RETURNING id, created_at, updated_at`,
-			channel.Name, channel.Description, channel.Status, modelMappingJSON, channel.BillingModelSource, channel.RestrictModels, channel.Features,
+			channel.Name, channel.Description, channel.Status, modelMappingJSON, channel.BillingModelSource, channel.RestrictModels, channel.Features, featuresConfigJSON,
 		).Scan(&channel.ID, &channel.CreatedAt, &channel.UpdatedAt)
 		if err != nil {
 			if isUniqueViolation(err) {
@@ -73,11 +77,11 @@ func (r *channelRepository) Create(ctx context.Context, channel *service.Channel
 
 func (r *channelRepository) GetByID(ctx context.Context, id int64) (*service.Channel, error) {
 	ch := &service.Channel{}
-	var modelMappingJSON []byte
+	var modelMappingJSON, featuresConfigJSON []byte
 	err := r.db.QueryRowContext(ctx,
-		`SELECT id, name, description, status, model_mapping, billing_model_source, restrict_models, features, created_at, updated_at
+		`SELECT id, name, description, status, model_mapping, billing_model_source, restrict_models, features, features_config, created_at, updated_at
 		 FROM channels WHERE id = $1`, id,
-	).Scan(&ch.ID, &ch.Name, &ch.Description, &ch.Status, &modelMappingJSON, &ch.BillingModelSource, &ch.RestrictModels, &ch.Features, &ch.CreatedAt, &ch.UpdatedAt)
+	).Scan(&ch.ID, &ch.Name, &ch.Description, &ch.Status, &modelMappingJSON, &ch.BillingModelSource, &ch.RestrictModels, &ch.Features, &featuresConfigJSON, &ch.CreatedAt, &ch.UpdatedAt)
 	if err == sql.ErrNoRows {
 		return nil, service.ErrChannelNotFound
 	}
@@ -85,6 +89,7 @@ func (r *channelRepository) GetByID(ctx context.Context, id int64) (*service.Cha
 		return nil, fmt.Errorf("get channel: %w", err)
 	}
 	ch.ModelMapping = unmarshalModelMapping(modelMappingJSON)
+	ch.FeaturesConfig = unmarshalFeaturesConfig(featuresConfigJSON)
 
 	groupIDs, err := r.GetGroupIDs(ctx, id)
 	if err != nil {
@@ -107,10 +112,14 @@ func (r *channelRepository) Update(ctx context.Context, channel *service.Channel
 		if err != nil {
 			return err
 		}
+		featuresConfigJSON, err := marshalFeaturesConfig(channel.FeaturesConfig)
+		if err != nil {
+			return err
+		}
 		result, err := tx.ExecContext(ctx,
-			`UPDATE channels SET name = $1, description = $2, status = $3, model_mapping = $4, billing_model_source = $5, restrict_models = $6, features = $7, updated_at = NOW()
-			 WHERE id = $8`,
-			channel.Name, channel.Description, channel.Status, modelMappingJSON, channel.BillingModelSource, channel.RestrictModels, channel.Features, channel.ID,
+			`UPDATE channels SET name = $1, description = $2, status = $3, model_mapping = $4, billing_model_source = $5, restrict_models = $6, features = $7, features_config = $8, updated_at = NOW()
+			 WHERE id = $9`,
+			channel.Name, channel.Description, channel.Status, modelMappingJSON, channel.BillingModelSource, channel.RestrictModels, channel.Features, featuresConfigJSON, channel.ID,
 		)
 		if err != nil {
 			if isUniqueViolation(err) {
@@ -187,9 +196,9 @@ func (r *channelRepository) List(ctx context.Context, params pagination.Paginati
 
 	// 查询 channel 列表
 	dataQuery := fmt.Sprintf(
-		`SELECT c.id, c.name, c.description, c.status, c.model_mapping, c.billing_model_source, c.restrict_models, c.features, c.created_at, c.updated_at
-		 FROM channels c WHERE %s ORDER BY c.id ASC LIMIT $%d OFFSET $%d`,
-		whereClause, argIdx, argIdx+1,
+		`SELECT c.id, c.name, c.description, c.status, c.model_mapping, c.billing_model_source, c.restrict_models, c.features, c.features_config, c.created_at, c.updated_at
+		 FROM channels c WHERE %s ORDER BY %s LIMIT $%d OFFSET $%d`,
+		whereClause, channelListOrderBy(params), argIdx, argIdx+1,
 	)
 	args = append(args, pageSize, offset)
 
@@ -203,11 +212,12 @@ func (r *channelRepository) List(ctx context.Context, params pagination.Paginati
 	var channelIDs []int64
 	for rows.Next() {
 		var ch service.Channel
-		var modelMappingJSON []byte
-		if err := rows.Scan(&ch.ID, &ch.Name, &ch.Description, &ch.Status, &modelMappingJSON, &ch.BillingModelSource, &ch.RestrictModels, &ch.Features, &ch.CreatedAt, &ch.UpdatedAt); err != nil {
+		var modelMappingJSON, featuresConfigJSON []byte
+		if err := rows.Scan(&ch.ID, &ch.Name, &ch.Description, &ch.Status, &modelMappingJSON, &ch.BillingModelSource, &ch.RestrictModels, &ch.Features, &featuresConfigJSON, &ch.CreatedAt, &ch.UpdatedAt); err != nil {
 			return nil, nil, fmt.Errorf("scan channel: %w", err)
 		}
 		ch.ModelMapping = unmarshalModelMapping(modelMappingJSON)
+		ch.FeaturesConfig = unmarshalFeaturesConfig(featuresConfigJSON)
 		channels = append(channels, ch)
 		channelIDs = append(channelIDs, ch.ID)
 	}
@@ -246,9 +256,34 @@ func (r *channelRepository) List(ctx context.Context, params pagination.Paginati
 	return channels, paginationResult, nil
 }
 
+func channelListOrderBy(params pagination.PaginationParams) string {
+	sortBy := strings.ToLower(strings.TrimSpace(params.SortBy))
+	sortOrder := strings.ToUpper(params.NormalizedSortOrder(pagination.SortOrderAsc))
+
+	var column string
+	switch sortBy {
+	case "":
+		column = "c.id"
+		sortOrder = "ASC"
+	case "id":
+		column = "c.id"
+	case "name":
+		column = "c.name"
+	case "status":
+		column = "c.status"
+	case "created_at":
+		column = "c.created_at"
+	default:
+		column = "c.id"
+		sortOrder = "ASC"
+	}
+
+	return fmt.Sprintf("%s %s, c.id %s", column, sortOrder, sortOrder)
+}
+
 func (r *channelRepository) ListAll(ctx context.Context) ([]service.Channel, error) {
 	rows, err := r.db.QueryContext(ctx,
-		`SELECT id, name, description, status, model_mapping, billing_model_source, restrict_models, features, created_at, updated_at FROM channels ORDER BY id`,
+		`SELECT id, name, description, status, model_mapping, billing_model_source, restrict_models, features, features_config, created_at, updated_at FROM channels ORDER BY id`,
 	)
 	if err != nil {
 		return nil, fmt.Errorf("query all channels: %w", err)
@@ -259,11 +294,12 @@ func (r *channelRepository) ListAll(ctx context.Context) ([]service.Channel, err
 	var channelIDs []int64
 	for rows.Next() {
 		var ch service.Channel
-		var modelMappingJSON []byte
-		if err := rows.Scan(&ch.ID, &ch.Name, &ch.Description, &ch.Status, &modelMappingJSON, &ch.BillingModelSource, &ch.RestrictModels, &ch.Features, &ch.CreatedAt, &ch.UpdatedAt); err != nil {
+		var modelMappingJSON, featuresConfigJSON []byte
+		if err := rows.Scan(&ch.ID, &ch.Name, &ch.Description, &ch.Status, &modelMappingJSON, &ch.BillingModelSource, &ch.RestrictModels, &ch.Features, &featuresConfigJSON, &ch.CreatedAt, &ch.UpdatedAt); err != nil {
 			return nil, fmt.Errorf("scan channel: %w", err)
 		}
 		ch.ModelMapping = unmarshalModelMapping(modelMappingJSON)
+		ch.FeaturesConfig = unmarshalFeaturesConfig(featuresConfigJSON)
 		channels = append(channels, ch)
 		channelIDs = append(channelIDs, ch.ID)
 	}
@@ -431,6 +467,28 @@ func unmarshalModelMapping(data []byte) map[string]map[string]string {
 	return m
 }
 
+func marshalFeaturesConfig(m map[string]any) ([]byte, error) {
+	if len(m) == 0 {
+		return []byte("{}"), nil
+	}
+	data, err := json.Marshal(m)
+	if err != nil {
+		return nil, fmt.Errorf("marshal features_config: %w", err)
+	}
+	return data, nil
+}
+
+func unmarshalFeaturesConfig(data []byte) map[string]any {
+	if len(data) == 0 {
+		return nil
+	}
+	var m map[string]any
+	if err := json.Unmarshal(data, &m); err != nil {
+		return nil
+	}
+	return m
+}
+
 // GetGroupPlatforms 批量查询分组 ID 对应的平台
 func (r *channelRepository) GetGroupPlatforms(ctx context.Context, groupIDs []int64) (map[int64]string, error) {
 	if len(groupIDs) == 0 {