What problem does this PR solve?

close #12770

This PR adds OceanBase as a storage backend for the Table Parser. It enables dynamic table schema storage via JSON and implements OceanBase SQL execution for text-to-SQL retrieval.

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

• Table Parser stores row data into chunk_data when doc engine is OceanBase. (table.py)
• OceanBase table schema adds chunk_data JSON column and migrates if needed.
• Implemented OceanBase sql() to execute text-to-SQL results. (ob_conn.py)
• Add DOC_ENGINE_OCEANBASE flag for engine detection (setting.py)

Test

1. Set DOC_ENGINE=oceanbase (e.g. in docker/.env)

2. Upload an Excel file to Knowledge Base.(for test, we use as below)

3. Choose Table as parsing method.

4.Ask a natural language query in chat.