feat(db): update SQL init script and Alembic migration for compatibility

Update data-annotation-init.sql and Alembic migration to support both new and old deployments:

SQL Initialization Script (data-annotation-init.sql):
- Add file_version column to t_dm_annotation_results table
- Add Alembic version table creation and version insertion
- New deployments using this script will have latest schema and Alembic version marked

Alembic Migration (20250205_0001_add_file_version.py):
- Add column_exists() helper function to detect if column already exists
- Add compatibility check in upgrade(): skip if column exists (new SQL init)
- Add informative print messages for deployment clarity
- Enhanced docstrings explaining compatibility strategy

Deployment Scenarios:
1. New deployment with latest SQL script: Schema created with file_version, Alembic marked as applied
2. Old deployment upgrade: Alembic detects missing column and adds it

This ensures backward compatibility while supporting fresh installs with complete schema.

scripts/db/data-annotation-init.sql

@@ -66,6 +66,7 @@ CREATE TABLE IF NOT EXISTS t_dm_annotation_results (
     file_id VARCHAR(36) NOT NULL COMMENT '文件ID',
     annotation JSON NOT NULL COMMENT 'Label Studio annotation 原始JSON',
     annotation_status VARCHAR(32) NOT NULL DEFAULT 'ANNOTATED' COMMENT '标注状态: ANNOTATED/NO_ANNOTATION/NOT_APPLICABLE',
+    file_version BIGINT NULL COMMENT '标注时的文件版本号',
     created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
     updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '更新时间',
     UNIQUE KEY uk_project_file (project_id, file_id),
@@ -1466,8 +1467,27 @@ INSERT INTO t_dm_annotation_templates (
     '1.0.0'
 );
 
+-- =============================================
+-- Alembic 版本控制表（标记数据库已应用最新迁移）
+-- 说明：如果使用此脚本初始化数据库，则不需要再运行 Alembic 升级
+-- =============================================
+
+-- 创建 alembic_version 表（如果不存在）
+CREATE TABLE IF NOT EXISTS alembic_version (
+    version_num VARCHAR(32) NOT NULL PRIMARY KEY
+) COMMENT='Alembic 迁移版本记录表';
+
+-- 清除现有版本记录（避免重复插入错误）
+DELETE FROM alembic_version;
+
+-- 插入当前最新版本（与 alembic/versions/20250205_0001_add_file_version.py 对应）
+INSERT INTO alembic_version (version_num) VALUES ('20250205_0001');
+
 -- =============================================
 -- 完成提示
 -- =============================================
 SELECT CONCAT('成功插入 ', COUNT(*), ' 个内置标注模板') AS result
 FROM t_dm_annotation_templates WHERE built_in = 1;
+
+SELECT CONCAT('数据库已初始化至 Alembic 版本: ', version_num) AS alembic_status
+FROM alembic_version;