feat: S0 主键改雪花（DDL 去 identity + 实体 ASSIGN_ID + 雪花配置）

为什么：自增主键把 ID 分配锁在单库序列上，分库分表时无法横向扩展。趁线上业务数据
近零（只有系统种子表有量）先改，代价最低。

- sql/schema.sql、sql/schema-phase1.sql、sql/partition-maintenance.sql：61 处
  GENERATED BY DEFAULT AS IDENTITY 去掉，主键改 BIGINT 无默认值
- 52 个实体 @TableId IdType.AUTO -> IdType.ASSIGN_ID；两个入口 id-type: assign_id，
  并加 global-config.sequence.worker-id/datacenter-id（单机固定值，多实例需按实例分配）
- 新增 sql/migrate-s0-snowflake.sql：存量库幂等迁移，走 DROP IDENTITY 保留数据，不重建表
- 实测：三份建表脚本在新库连跑两遍幂等；线上 57 张表 identity 归零；
  watch_history/playback_ticket/order_event 的主键与唯一索引仍含分区键

fruitshorts-module-interaction/src/main/java/com/fruitshorts/interaction/dal/entity/ContentAuditRecord.java

@@ -15,7 +15,7 @@ import java.time.LocalDateTime;
 @TableName("content_audit_record")
 public class ContentAuditRecord {
 
-    @TableId(type = IdType.AUTO)
+    @TableId(type = IdType.ASSIGN_ID)
     private Long id;
     /** COMMENT/DRAMA/AVATAR/CREATOR */
     private String bizType;

fruitshorts-module-interaction/src/main/java/com/fruitshorts/interaction/dal/entity/ContentComment.java

@@ -15,7 +15,7 @@ import java.time.LocalDateTime;
 @TableName("content_comment")
 public class ContentComment {
 
-    @TableId(type = IdType.AUTO)
+    @TableId(type = IdType.ASSIGN_ID)
     private Long id;
     private Long dramaId;
     private Long episodeId;

fruitshorts-module-interaction/src/main/java/com/fruitshorts/interaction/dal/entity/ContentLike.java

@@ -13,7 +13,7 @@ import java.time.LocalDateTime;
 @TableName("content_like")
 public class ContentLike {
 
-    @TableId(type = IdType.AUTO)
+    @TableId(type = IdType.ASSIGN_ID)
     private Long id;
     private Long userId;
     /** DRAMA/EPISODE/COMMENT */

fruitshorts-module-interaction/src/main/java/com/fruitshorts/interaction/dal/entity/ContentReport.java

@@ -15,7 +15,7 @@ import java.time.LocalDateTime;
 @TableName("content_report")
 public class ContentReport {
 
-    @TableId(type = IdType.AUTO)
+    @TableId(type = IdType.ASSIGN_ID)
     private Long id;
     private Long reporterId;
     /** COMMENT/USER/DRAMA */

fruitshorts-module-interaction/src/main/java/com/fruitshorts/interaction/dal/entity/ContentShare.java

@@ -12,7 +12,7 @@ import java.time.LocalDateTime;
 @TableName("content_share")
 public class ContentShare {
 
-    @TableId(type = IdType.AUTO)
+    @TableId(type = IdType.ASSIGN_ID)
     private Long id;
     private Long userId;
     private Long dramaId;

fruitshorts-module-interaction/src/main/java/com/fruitshorts/interaction/dal/entity/SensitiveWord.java

@@ -15,7 +15,7 @@ import java.time.LocalDateTime;
 @TableName("sensitive_word")
 public class SensitiveWord {
 
-    @TableId(type = IdType.AUTO)
+    @TableId(type = IdType.ASSIGN_ID)
     private Long id;
     private String word;
     /** POLITICS/PORN/ABUSE/AD/RELIGION */

fruitshorts-module-interaction/src/main/java/com/fruitshorts/interaction/dal/entity/UserBlocklist.java

@@ -13,7 +13,7 @@ import java.time.LocalDateTime;
 @TableName("user_blocklist")
 public class UserBlocklist {
 
-    @TableId(type = IdType.AUTO)
+    @TableId(type = IdType.ASSIGN_ID)
     private Long id;
     private Long userId;
     private Long blockedUserId;