移除"从素材提取尾帧"功能（上游已实现类似功能）

- 移除 ExtractFrame handler 和路由
- 移除 AssetService 中的 ExtractFrameFromAsset 方法
- 移除 FFmpeg 中的 ExtractFrame 方法
- 移除前端 extractFrame API 和相关 UI

Co-Authored-By: Claude <noreply@anthropic.com>

api/handlers/asset.go

@@ -218,27 +218,3 @@ func (h *AssetHandler) ImportFromVideoGen(c *gin.Context) {
 
 	response.Success(c, asset)
 }
-
-// ExtractFrame 从视频素材中提取帧
-func (h *AssetHandler) ExtractFrame(c *gin.Context) {
-	assetID, err := strconv.ParseUint(c.Param("id"), 10, 32)
-	if err != nil {
-		response.BadRequest(c, "无效的ID")
-		return
-	}
-
-	var req services.ExtractFrameRequest
-	if err := c.ShouldBindJSON(&req); err != nil {
-		response.BadRequest(c, err.Error())
-		return
-	}
-
-	imageGen, err := h.assetService.ExtractFrameFromAsset(uint(assetID), &req)
-	if err != nil {
-		h.log.Errorw("Failed to extract frame", "error", err, "asset_id", assetID)
-		response.InternalError(c, err.Error())
-		return
-	}
-
-	response.Success(c, imageGen)
-}

api/routes/routes.go

@@ -181,7 +181,6 @@ func SetupRouter(cfg *config.Config, db *gorm.DB, log *logger.Logger, localStora
 			assets.DELETE("/:id", assetHandler.DeleteAsset)
 			assets.POST("/import/image/:image_gen_id", assetHandler.ImportFromImageGen)
 			assets.POST("/import/video/:video_gen_id", assetHandler.ImportFromVideoGen)
-			assets.POST("/:id/extract-frame", assetHandler.ExtractFrame)
 		}
 
 		storyboards := api.Group("/storyboards")