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

cmd/server/main.go

@@ -22,6 +22,9 @@ type modelResponse struct {
 	ProviderCN     string  `json:"providerCN"`
 	Modality       string  `json:"modality"`
 	ContextLength  int     `json:"contextLength"`
+	PricingMode    string  `json:"pricingMode,omitempty"`
+	PriceUnit      string  `json:"priceUnit,omitempty"`
+	FlatPrice      float64 `json:"flatPrice,omitempty"`
 	InputPrice     float64 `json:"inputPrice"`
 	OutputPrice    float64 `json:"outputPrice"`
 	Currency       string  `json:"currency"`
@@ -171,6 +174,9 @@ func fetchModels(ctx context.Context, db *sql.DB) ([]modelResponse, error) {
 		WITH latest_prices AS (
 			SELECT
 				rp.model_id,
+				rp.pricing_mode,
+				rp.price_unit,
+				rp.flat_price,
 				rp.input_price_per_mtok,
 				rp.output_price_per_mtok,
 				rp.currency,
@@ -188,6 +194,9 @@ func fetchModels(ctx context.Context, db *sql.DB) ([]modelResponse, error) {
 			COALESCE(mp.name, split_part(m.external_id, '/', 1)),
 			COALESCE(m.modality, 'text'),
 			COALESCE(m.context_length, 0),
+			COALESCE(lp.pricing_mode, 'input_output'),
+			COALESCE(lp.price_unit, 'million_tokens'),
+			COALESCE(lp.flat_price, 0),
 			lp.input_price_per_mtok,
 			lp.output_price_per_mtok,
 			COALESCE(lp.currency, 'USD'),
@@ -207,6 +216,7 @@ func fetchModels(ctx context.Context, db *sql.DB) ([]modelResponse, error) {
 	var models []modelResponse
 	for rows.Next() {
 		var model modelResponse
+		var flatPrice sql.NullFloat64
 		var inputPrice sql.NullFloat64
 		var outputPrice sql.NullFloat64
 		if err := rows.Scan(
@@ -216,6 +226,9 @@ func fetchModels(ctx context.Context, db *sql.DB) ([]modelResponse, error) {
 			&model.Provider,
 			&model.Modality,
 			&model.ContextLength,
+			&model.PricingMode,
+			&model.PriceUnit,
+			&flatPrice,
 			&inputPrice,
 			&outputPrice,
 			&model.Currency,
@@ -232,6 +245,9 @@ func fetchModels(ctx context.Context, db *sql.DB) ([]modelResponse, error) {
 		if outputPrice.Valid {
 			model.OutputPrice = outputPrice.Float64
 		}
+		if flatPrice.Valid {
+			model.FlatPrice = flatPrice.Float64
+		}
 		model.Stale = model.DataConfidence == "stale"
 		models = append(models, model)
 	}