refactor(video): 预置 AI 算法改为 SQL 种子数据，移除 @PostConstruct 初始化

原 AiAlgorithmServiceImpl.initPresetAlgorithms() 在 @PostConstruct
里插入 4 条预置算法，带来两个问题：
1. 启动时无登录上下文，MP 自动填充 creator 失效 → 启动失败
2. 算法清单硬编码在 Java 代码，迭代要重编译发布

改为 video.sql 种子数据管理：
- video.sql 的预置算法 INSERT 扩展为 4 条（leave_post / intrusion /
  illegal_parking / vehicle_congestion），参数 schema 与边缘端对齐
- 使用 ON DUPLICATE KEY UPDATE 保证幂等：新库初始化 + 存量库升级
  都走同一条语句，param_schema / description 会被自动校正
- 保留用户侧可修改的字段（is_active / global_params）不被覆盖

代码层：
- 删除 initPresetAlgorithms() 方法与 PRESET_ALGORITHMS 静态 Map
- 删除 SYSTEM_USER 常量
- 删除 @PostConstruct / HashMap 相关 import
- 保留 syncFromEdge() 作为边缘端主动同步的运行时入口

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

sql/mysql/video.sql

@@ -935,12 +935,30 @@ CREATE TABLE `video_ai_algo_template` (
 -- ============================================================================
 
 -- 预置算法（与 FastAPI 边缘端保持一致）
+-- 幂等：已存在则更新 name/target_class/param_schema/description，保持 is_active 与用户设置
 INSERT INTO `video_ai_algorithm` (`algo_code`, `algo_name`, `target_class`, `param_schema`, `description`, `is_active`, `creator`, `create_time`, `updater`, `update_time`, `deleted`, `tenant_id`) VALUES
 ('leave_post', '离岗检测', 'person',
- '{"confirm_on_duty_sec":{"type":"int","default":10,"min":1},"confirm_leave_sec":{"type":"int","default":30,"min":1},"leave_countdown_sec":{"type":"int","default":300,"min":0},"cooldown_sec":{"type":"int","default":600,"min":0},"working_hours":{"type":"list","default":[]}}',
- '检测人员是否在岗，支持工作时间段配置', 1, 'system', NOW(), 'system', NOW(), b'0', 0),
+ '{"leave_countdown_sec":{"type":"int","default":300,"min":0},"working_hours":{"type":"list","default":[]}}',
+ '检测人员是否在岗，支持工作时间段配置。算法抽帧频率：3帧/秒（固定）',
+ 1, '1', NOW(), '1', NOW(), b'0', 0),
 ('intrusion', '周界入侵检测', 'person',
- '{"cooldown_seconds":{"type":"int","default":120,"min":0},"confirm_seconds":{"type":"int","default":5,"min":1}}',
- '检测人员进入指定区域', 1, 'system', NOW(), 'system', NOW(), b'0', 0);
+ '{"cooldown_seconds":{"type":"int","default":300,"min":0},"confirm_seconds":{"type":"int","default":5,"min":1},"confirm_intrusion_seconds":{"type":"int","default":5,"min":1},"confirm_clear_seconds":{"type":"int","default":180,"min":1}}',
+ '检测人员进入指定区域。算法抽帧频率：1帧/秒（固定）。持续检测到人5秒触发告警，持续无人180秒自动结束告警。消失确认期间短暂有人(<5秒)不影响倒计时。',
+ 1, '1', NOW(), '1', NOW(), b'0', 0),
+('illegal_parking', '车辆违停检测', 'car,truck,bus,motorcycle',
+ '{"confirm_vehicle_sec":{"type":"int","default":15,"min":5},"parking_countdown_sec":{"type":"int","default":300,"min":60},"confirm_clear_sec":{"type":"int","default":30,"min":10},"cooldown_sec":{"type":"int","default":600,"min":0}}',
+ '检测禁停区域内是否有车辆违规停放。确认车辆停留15秒后开始5分钟倒计时，超时触发告警。车辆离开30秒后自动结束告警。',
+ 1, '1', NOW(), '1', NOW(), b'0', 0),
+('vehicle_congestion', '车辆拥堵检测', 'car,truck,bus,motorcycle',
+ '{"count_threshold":{"type":"int","default":3,"min":1},"confirm_congestion_sec":{"type":"int","default":60,"min":10},"confirm_clear_sec":{"type":"int","default":120,"min":10},"cooldown_sec":{"type":"int","default":600,"min":0}}',
+ '检测区域内车辆是否拥堵。当平均车辆数达到阈值并持续60秒触发告警，车辆减少并持续120秒后自动结束告警。',
+ 1, '1', NOW(), '1', NOW(), b'0', 0)
+ON DUPLICATE KEY UPDATE
+    `algo_name`    = VALUES(`algo_name`),
+    `target_class` = VALUES(`target_class`),
+    `param_schema` = VALUES(`param_schema`),
+    `description`  = VALUES(`description`),
+    `updater`      = VALUES(`updater`),
+    `update_time`  = NOW();
 
 SET FOREIGN_KEY_CHECKS = 1;