Add tencentcloud_search tool

[jayeeliu]

Summary

Search tool using Tencent Cloud Web Search API (WSA) for users in China.

Checklist

• [✔] Tested locally
• [✔] No unrelated changes included

[wisdomqin]

Thanks for the PR. Please split this into separate PRs:

1. One PR for the Tencent Cloud Search tool.
2. One PR for the Alembic migration fixes, with the exact migration failure scenario included.

The migration changes need extra care. In particular, the change to add_participants.py appears to join identities, but that table is created later in the migration chain, so this may break fresh installs.

For the search tool: the direction is fine, but please keep it as a standalone tool. Our search tools are no longer merged into the old web_search engine selector; each provider should be exposed as its own dedicated tool. So the web_search Tencent Cloud branch should be removed unless the full legacy config path is intentionally supported.

Thanks again.

[jayeeliu]

Thanks for the PR. Please split this into separate PRs:

1. One PR for the Tencent Cloud Search tool.
2. One PR for the Alembic migration fixes, with the exact migration failure scenario included.

The migration changes need extra care. In particular, the change to add_participants.py appears to join identities, but that table is created later in the migration chain, so this may break fresh installs.

For the search tool: the direction is fine, but please keep it as a standalone tool. Our search tools are no longer merged into the old web_search engine selector; each provider should be exposed as its own dedicated tool. So the web_search Tencent Cloud branch should be removed unless the full legacy config path is intentionally supported.

Thanks again.

This PR for Tencent Cloud Search tool. I've removed tencentcloud search from web_search.

I encountered alembic update error when upgrading Clawith from 1.8.2 to 1.8.3-beta.2.
When executing docker exec clawith-backend-1 alembic upgrade heads, I faced roughly 4 errors. I fixed each by following the error message until the upgrade succeeded.
I’m still getting familiar with Clawith and my time is tight recently. I’ll submit search tool PR first and handle the other one later.

Thank you for providing such a useful tool !