feat(region_pricing): 扩展非 token 统一计费字段，支持语音按字符/秒计费

- 新增 region_pricing.pricing_mode / price_unit / flat_price 字段
- 新增 migration 016_region_pricing_non_token_units.sql
- officialPricingRecord 新增 PricingMode/PriceUnit/FlatPrice 字段
- detectModality 新增 audio 模态检测（voice/audio/speech）
- providerMetadata 新增 BAAI/ByteDance/China Mobile 元数据
- import_mobile_cloud_pricing.go: 解析语音计费表（CosyVoice/SenseVoice）
  - CosyVoice: 2元/万字符 → pricingMode=flat, priceUnit=10k_characters
  - SenseVoice: 0.0007元/秒 → pricingMode=flat, priceUnit=second
- mobileCloudProviderName 新增 cosyvoice/sensevoice → Alibaba 映射
- cmd/server: modelResponse 新增 pricingMode/priceUnit/flatPrice，API 字段说明同步更新
- 新增 TestModelsHandlerReturnsFlatPricingFields 测试

scripts/official_pricing_import_common.go

@@ -34,6 +34,9 @@ type officialPricingRecord struct {
 	OperatorType    string
 	Region          string
 	Currency        string
+	PricingMode     string
+	PriceUnit       string
+	FlatPrice       float64
 	InputPrice      float64
 	OutputPrice     float64
 	ContextLength   int
@@ -81,16 +84,21 @@ func upsertOfficialPricingRecords(db *sql.DB, records []officialPricingRecord, b
 		_, err = db.Exec(
 			`INSERT INTO region_pricing (
 				model_id, operator_id, region, currency,
+				pricing_mode, price_unit, flat_price,
 				input_price_per_mtok, output_price_per_mtok,
 				is_free, effective_date, source_url, source_type,
 				free_quota, free_limitations, rate_limit
 			) VALUES (
 				$1, $2, $3, $4,
-				$5, $6, $7, CURRENT_DATE, $8, $9,
-				$10, $11, $12
+				$5, $6, $7,
+				$8, $9, $10, CURRENT_DATE, $11, $12,
+				$13, $14, $15
 			)
 			ON CONFLICT (model_id, operator_id, region, currency, effective_date)
 			DO UPDATE SET
+				pricing_mode = EXCLUDED.pricing_mode,
+				price_unit = EXCLUDED.price_unit,
+				flat_price = EXCLUDED.flat_price,
 				input_price_per_mtok = EXCLUDED.input_price_per_mtok,
 				output_price_per_mtok = EXCLUDED.output_price_per_mtok,
 				is_free = EXCLUDED.is_free,
@@ -101,6 +109,7 @@ func upsertOfficialPricingRecords(db *sql.DB, records []officialPricingRecord, b
 				rate_limit = EXCLUDED.rate_limit,
 				updated_at = CURRENT_TIMESTAMP`,
 			modelID, operatorID, record.Region, record.Currency,
+			fallbackPricingMode(record.PricingMode), fallbackPriceUnit(record.PriceUnit), nullIfZeroFloat(record.FlatPrice),
 			record.InputPrice, record.OutputPrice, record.IsFree, record.SourceURL, sourceType,
 			nullIfBlank(freeQuota), freeLimitations, rateLimit,
 		)
@@ -260,6 +269,29 @@ func fallbackModality(raw string) string {
 	return value
 }
 
+func fallbackPricingMode(raw string) string {
+	value := strings.TrimSpace(raw)
+	if value == "" {
+		return "input_output"
+	}
+	return value
+}
+
+func fallbackPriceUnit(raw string) string {
+	value := strings.TrimSpace(raw)
+	if value == "" {
+		return "million_tokens"
+	}
+	return value
+}
+
+func nullIfZeroFloat(value float64) any {
+	if value == 0 {
+		return nil
+	}
+	return value
+}
+
 func fetchRawPricingPage(url string, fixture string, client *http.Client) (string, error) {
 	return fetchRawPricingPageWithOptions(url, fixture, client, officialPricingFetchOptions{
 		AcceptLanguage: "zh-CN,zh;q=0.9,en;q=0.8",
@@ -399,6 +431,8 @@ func detectModality(modelName string) string {
 	switch {
 	case strings.Contains(lower, "coder"), strings.Contains(lower, "code"):
 		return "code"
+	case strings.Contains(lower, "voice"), strings.Contains(lower, "audio"), strings.Contains(lower, "speech"):
+		return "audio"
 	case strings.Contains(lower, "vision"), strings.Contains(lower, "vl"), strings.Contains(lower, "omni"), strings.Contains(lower, "multi"), strings.Contains(lower, "live"):
 		return "multimodal"
 	default:
@@ -414,8 +448,14 @@ func providerMetadata(providerName string) (string, string, string) {
 		return "亚马逊", "US", "https://aws.amazon.com"
 	case "Anthropic":
 		return "Anthropic", "US", "https://www.anthropic.com"
+	case "BAAI":
+		return "智源", "CN", "https://www.baai.ac.cn"
 	case "Baidu":
 		return "百度", "CN", "https://cloud.baidu.com"
+	case "ByteDance":
+		return "字节跳动", "CN", "https://www.volcengine.com"
+	case "China Mobile":
+		return "中国移动", "CN", "https://ecloud.10086.cn"
 	case "Cloudflare":
 		return "Cloudflare", "US", "https://www.cloudflare.com"
 	case "Cohere":