feat(utils): add configurable ID factory via set_id_factory()

[lajxw]

AgentScope Version

2.0.1

Description

Background: AgentScope hardcodes uuid.uuid4().hex for all entity IDs. This prevents alignment with production databases that use other ID strategies such as UUIDv7 (time-ordered), causing block_id mismatch between streaming events and persisted records.

Changes:
- Added _id_factory global and set_id_factory() in src/agentscope/_utils/_common.py, allowing users to override the default ID generation strategy at startup.
- Exported set_id_factory from src/agentscope/init.py as public API.
- Replaced 34 occurrences of uuid.uuid4().hex with _generate_id / _generate_id() across 18 entity files.
- Security-sensitive tokens (gateway tokens, Redis lock tokens) intentionally remain as uuid.uuid4().hex.

Close #1782

Checklist

Please check the following items before code is ready to be reviewed.

• An issue has been created for this PR
• I have read the CONTRIBUTING.md
• Docstrings are in Google style
• Related documentation has been updated (e.g. links, examples, etc.) in documentation repository
• Code is ready for review

[DavdGao]

Thanks for the PR. Two suggestions on the test file:

1. Make the tests async to match our template. Please follow tests/test_template.py, which uses IsolatedAsyncioTestCase with asyncSetUp / asyncTearDown instead of the sync unittest.TestCase.
2. Trim the test cases. A few of the current tests add little value (e.g. asserting the public export is the internal function, the non-callable TypeError check). Please keep just the two that capture the intent:

• the default id_factory still returns uuid.uuid4().hex
• after from agentscope import set_id_factory, a custom factory actually takes effect on entities

[DavdGao]

@lajxw Plz format the code by running pre-commit run --all-files

[lajxw]

I have made the requested changes; please review again.

[DavdGao]

LGTM