fix(aihr): recover stalled media processing

backend/script/sql/update/aihr_20260729_media_reprocess_mysql8.sql

@@ -0,0 +1,36 @@
+-- 资料处理媒体重试：记录从既有知识附件重新解析的来源，支持直接从 OSS 原件重新入队。
+-- 可重复执行；依赖 aihr_knowledge_upload_item。
+
+SET @has_source_attach_id := (
+  SELECT COUNT(*) FROM information_schema.columns
+  WHERE table_schema = DATABASE()
+    AND table_name = 'aihr_knowledge_upload_item'
+    AND column_name = 'source_attach_id'
+);
+SET @media_reprocess_ddl := IF(
+  @has_source_attach_id = 0,
+  'ALTER TABLE aihr_knowledge_upload_item ADD COLUMN source_attach_id bigint DEFAULT NULL COMMENT ''从既有附件重新解析时的附件ID'' AFTER staging_path',
+  'SELECT 1'
+);
+PREPARE media_reprocess_stmt FROM @media_reprocess_ddl;
+EXECUTE media_reprocess_stmt;
+DEALLOCATE PREPARE media_reprocess_stmt;
+
+SET @has_media_source_index := (
+  SELECT COUNT(*) FROM information_schema.statistics
+  WHERE table_schema = DATABASE()
+    AND table_name = 'aihr_knowledge_upload_item'
+    AND index_name = 'idx_aihr_upload_item_source'
+);
+SET @media_reprocess_ddl := IF(
+  @has_media_source_index = 0,
+  'ALTER TABLE aihr_knowledge_upload_item ADD KEY idx_aihr_upload_item_source (tenant_id, source_attach_id, id)',
+  'SELECT 1'
+);
+PREPARE media_reprocess_stmt FROM @media_reprocess_ddl;
+EXECUTE media_reprocess_stmt;
+DEALLOCATE PREPARE media_reprocess_stmt;
+
+SET @has_source_attach_id := NULL;
+SET @has_media_source_index := NULL;
+SET @media_reprocess_ddl := NULL;