feat: 支持视频及缩略图元数据存储

在文件服务和故事服务中增加了对视频、持续时间及缩略图相关字段的支持。

- 在 `ImageInfo` 和 `StoryItem` 实体类中添加 `duration`、`thumbnailInstanceId` 等字段
- 更新 MyBatis 映射文件以支持新字段的持久化
- 在 `FileService` 中新增 `generateVideoUrl` 接口用于获取视频预签名地址
- 调整 `saveFileMetadata` 接口返回生成的 `instanceId`
- 优化了部分代码的格式和缩进

timeline-story-service/src/main/java/com/timeline/story/entity/StoryItem.java

@@ -14,6 +14,9 @@ public class StoryItem {
     private String description;
     private String location;
     private LocalDateTime storyItemTime;
+    private String videoUrl;
+    private Long duration;
+    private String thumbnailUrl;
     private String createId;
     private String updateId;
     private LocalDateTime createTime;

timeline-story-service/src/main/resources/com/timeline/story/dao/StoryItemMapper.xml

@@ -5,8 +5,8 @@
 <mapper namespace="com.timeline.story.dao.StoryItemMapper">
 
     <insert id="insert">
-        INSERT INTO story_item (instance_id, master_item_id, description, location, title, create_id, story_instance_id, is_delete, story_item_time, update_id)
-        VALUES (#{instanceId}, #{masterItemId}, #{description}, #{location}, #{title},#{createId}, #{storyInstanceId}, #{isDelete}, #{storyItemTime}, #{updateId})
+        INSERT INTO story_item (instance_id, master_item_id, description, location, title, create_id, story_instance_id, is_delete, story_item_time, update_id, video_url, duration, thumbnail_url)
+        VALUES (#{instanceId}, #{masterItemId}, #{description}, #{location}, #{title},#{createId}, #{storyInstanceId}, #{isDelete}, #{storyItemTime}, #{updateId}, #{videoUrl}, #{duration}, #{thumbnailUrl})
     </insert>
 
     <update id="update">
@@ -16,7 +16,10 @@
             title = #{title},
             create_id = #{createId},
             update_time = NOW(),
-            update_id = #{updateId}
+            update_id = #{updateId},
+            video_url = #{videoUrl},
+            duration = #{duration},
+            thumbnail_url = #{thumbnailUrl}
         WHERE instance_id = #{instanceId}
     </update>
 
@@ -48,6 +51,9 @@
             si.master_item_id,
             si.is_delete,
             si.story_item_time as story_item_time,
+            si.video_url,
+            si.duration,
+            si.thumbnail_url,
             si.create_id AS create_id,
             si.create_time AS create_time,
             u1.username AS create_name,