[Bug] 事务修复后偶现 Session 无法删除的问题（即使已清空所有外链数据） / Session cannot be deleted occasionally after transaction fix for deadlocks (even after clearing all foreign-linked data)

[SunYanbox]

描述 / Description
在使用事务机制修复多进程数据库死锁问题后，大部分场景下 Session 能够被正确删除。但存在一定概率，某个 Session 即使其所有外键关联的数据（外链数据）都已被手动清空，依然无法被删除操作移除，且不报任何显式错误或仅返回“影响行数为 0”。
After fixing multi-process database deadlocks with transaction mechanisms, most sessions can be deleted correctly. However, with a certain probability, a session remains undeletable even after all its foreign-key-linked data has been manually cleared. The delete operation either fails silently or returns “0 rows affected” without an explicit error.

期望行为 / Expected Behavior
一旦 Session 的所有外链依赖数据被清空，对应的 Session 记录应当能够被正常删除，不应出现一直残留且无法删除的情况。
Once all foreign-key dependent data of a session is cleared, the corresponding session record should be deletable without permanent retention.

实际行为 / Actual Behavior
特定 Session 无法被删除，即使确认其关联的外键表已无任何引用。该 Session 记录依然存在于表中。
A specific session cannot be deleted even after confirming there are no remaining references in foreign-key tables. The session record persists in the table.

After #117

低优先级, 因为此情景出现次数少且难以复现 / Low priority — rare and hard to reproduce