feat(cryptotail): 尾盘 TG 改为轮询实现并修复自调用

- 新增 notification_sent 字段与 V36 迁移，轮询未发 TG 的 trigger
- 新增 CryptoTailOrderNotificationPollingService：每 5 秒轮询，CLOB getOrder 后发 TG，与跟单一致
- 通过 ApplicationContextAware + getSelf() 解决 @Transactional 自调用问题
- 删除 CryptoTailOrderNotificationSubscriber，移除 WS 推送方式
- Repository 新增 findByStatusAndOrderIdIsNotNullAndNotificationSentFalseOrderByCreatedAtAsc

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/src/main/resources/db/migration/V36__add_crypto_tail_trigger_notification_sent.sql

@@ -0,0 +1,8 @@
+-- ============================================
+-- V36: 尾盘策略触发记录 - TG 通知已发标记（与跟单轮询发 TG 一致）
+-- ============================================
+
+ALTER TABLE crypto_tail_strategy_trigger
+    ADD COLUMN notification_sent TINYINT(1) NOT NULL DEFAULT 0 COMMENT '是否已发送 TG 通知: 0=未发送, 1=已发送';
+
+CREATE INDEX idx_trigger_notification ON crypto_tail_strategy_trigger (status, notification_sent);