What problem does this PR solve?

Close #12768.

This PR adds OceanBase support to RAGFlow’s Text-to-SQL (ExeSQL) component.
OceanBase is integrated via MySQL compatibility mode, and the UI db_type options are updated accordingly.

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

Changes

Backend

• Add oceanbase db_type validation and connection logic in exesql.py and reuse existing MySQL compatibility mode

Frontend

• Add OceanBase option to the ExeSQL db_type selector

How to test

1. Configure OceanBase connection in ExeSQL node (host/port/user/password/database)
2. Input: “Show 10 rows from test table”
3. Generated SQL: SELECT * FROM test LIMIT 10;
4. Query executes successfully and results are returned

Screenshots

• ExeSQL db_type includes OceanBase

• ExeSQL test OceanBase connection

• Query results from OceanBase shown in UI