feat(example): add MOSProduct multi-user locomo example with shared Neo4j database

[CaralHsi]

Description

Summary:

• Added a new example locomo_shared_database_memos.py under examples/mem_os/
• Demonstrates how to use MOSProduct to manage multiple users in locomo
• Both users share the same Neo4j database with isolated user_id and cube_id namespaces
• Conversation messages are processed with dual-perspective role mapping (user ↔ assistant)
• Uses SimpleStructMemReader with chunker + universal embedder for flexible LLM + embedding workflow
• Includes clear logging for each session and message for easier debugging

Reviewer: @fridayL

Checklist:

• I have performed a self-review of my own code | 我已自行检查了自己的代码
• I have commented my code in hard-to-understand areas | 我已在难以理解的地方对代码进行了注释
• I have added tests that prove my fix is effective or that my feature works | 我已添加测试以证明我的修复有效或功能正常
• I have added necessary documentation (if applicable) | 我已添加必要的文档（如果适用）
• I have linked the issue to this PR (if applicable) | 我已将 issue 链接到此 PR（如果适用）
• I have mentioned the person who will review this PR | 我已提及将审查此 PR 的人

[fridayL]

mos_product.add(user_id=users[speaker_a]["user_id"], messages=role1_msgs)
mos_product.add(user_id=users[speaker_b]["user_id"], messages=role2_msgs)

this code doesn't seem to cause errors, but For multi-user operations on diff cubes, it's better to input cube ID ：
mos_product.add(user_id=users[speaker_a]["user_id"], messages=role1_msgs， mem_cube_id=users[speaker_a]["default_cube_id"])

[CaralHsi]

Okkk, I see. Will update soon.

[CaralHsi]

@J1awei-Yang Please fix 'never close' issue for this.