fix: 删除 graph-service 中重复的 Template 实体和 Repository

删除文件：
- graph-service/.../entity/Template.java
- graph-service/.../repository/TemplateRepository.java

原因：与 extract-service 中新版模板系统 Bean 名称冲突
模板系统已迁移至 extract-service

backend/graph-service/src/main/java/com/lingyue/graph/entity/Template.java

@@ -1,51 +0,0 @@
-package com.lingyue.graph.entity;
-
-import com.baomidou.mybatisplus.annotation.TableField;
-import com.baomidou.mybatisplus.annotation.TableName;
-import com.lingyue.common.mybatis.PostgreSqlJsonbTypeHandler;
-import com.lingyue.common.domain.entity.SimpleModel;
-import io.swagger.v3.oas.annotations.media.Schema;
-import lombok.Data;
-import lombok.EqualsAndHashCode;
-
-/**
- * 模板实体
- * 用于管理报告模板和占位符映射
- * 
- * @author lingyue
- * @since 2026-01-14
- */
-@EqualsAndHashCode(callSuper = true)
-@Data
-@TableName(value = "templates", autoResultMap = true)
-@Schema(description = "模板实体")
-public class Template extends SimpleModel {
-    
-    @Schema(description = "用户ID")
-    @TableField("user_id")
-    private String userId;
-    
-    @Schema(description = "模板名称")
-    @TableField("name")
-    private String name;
-    
-    @Schema(description = "模板内容（带占位符）")
-    @TableField("content")
-    private String content;
-    
-    @Schema(description = "占位符映射", example = "{\"{{ds1}}\": \"dataSourceId1\"}")
-    @TableField(value = "placeholder_mapping", typeHandler = PostgreSqlJsonbTypeHandler.class)
-    private Object placeholderMapping;
-    
-    @Schema(description = "复制来源模板ID")
-    @TableField("source_template_id")
-    private String sourceTemplateId;
-    
-    @Schema(description = "状态", example = "active/inactive")
-    @TableField("status")
-    private String status = "active";
-    
-    @Schema(description = "元数据")
-    @TableField(value = "metadata", typeHandler = PostgreSqlJsonbTypeHandler.class)
-    private Object metadata;
-}

backend/graph-service/src/main/java/com/lingyue/graph/repository/TemplateRepository.java

@@ -1,47 +0,0 @@
-package com.lingyue.graph.repository;
-
-import com.baomidou.mybatisplus.core.mapper.BaseMapper;
-import com.lingyue.graph.entity.Template;
-import org.apache.ibatis.annotations.Mapper;
-import org.apache.ibatis.annotations.Param;
-import org.apache.ibatis.annotations.Select;
-
-import java.util.List;
-
-/**
- * 模板Repository
- * 
- * @author lingyue
- * @since 2026-01-14
- */
-@Mapper
-public interface TemplateRepository extends BaseMapper<Template> {
-    
-    /**
-     * 根据用户ID查询模板列表
-     * 
-     * @param userId 用户ID
-     * @return 模板列表
-     */
-    @Select("SELECT * FROM templates WHERE user_id = #{userId} ORDER BY create_time DESC")
-    List<Template> findByUserId(@Param("userId") String userId);
-    
-    /**
-     * 根据用户ID和状态查询模板
-     * 
-     * @param userId 用户ID
-     * @param status 状态
-     * @return 模板列表
-     */
-    @Select("SELECT * FROM templates WHERE user_id = #{userId} AND status = #{status} ORDER BY create_time DESC")
-    List<Template> findByUserIdAndStatus(@Param("userId") String userId, @Param("status") String status);
-    
-    /**
-     * 根据来源模板ID查询衍生模板
-     * 
-     * @param sourceTemplateId 来源模板ID
-     * @return 模板列表
-     */
-    @Select("SELECT * FROM templates WHERE source_template_id = #{sourceTemplateId}")
-    List<Template> findBySourceTemplateId(@Param("sourceTemplateId") String sourceTemplateId);
-}