Squashed commit of the following:

Squashed commit of the following:

commit 24ff4a8bbac71a174d6d7a2ab319fdf9bae04e6f
Author: yuanoOo <zhaomingyuan.zmy@digital-engine.com>
Date:   Sun Sep 28 16:28:57 2025 +0800

    docs: Add OceanBase SQLAlchemy plugin to dialects documentation

    - Add OceanBase entry to External Dialects table
    - Add link to oceanbase-sqlalchemy plugin repository
    - References: https://github.com/oceanbase/ecology-plugins/tree/main/oceanbase-sqlalchemy-plugin

Change-Id: I6d99421e5e931d8306416e3afdb14e65e88f9be1
(cherry picked from commit 828ca9d243b3a3af26a4543b1a2ad8bc036f0758)