feature:Add OceanBase Storage Support for Table Parser (#12923)

### 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)
- [x] 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`)
<img width="1290" height="783" alt="doc_engine_ob"
src="https://github.com/user-attachments/assets/7d1c609f-7bf2-4b2e-b4cc-4243e72ad4f1"
/>

2. Upload an Excel file to Knowledge Base.(for test, we use as below)
<img width="786" height="930" alt="excel"
src="https://github.com/user-attachments/assets/bedf82f2-cd00-426b-8f4d-6978a151231a"
/>

3. Choose **Table** as parsing method.
<img width="2550" height="1134" alt="parse_excel"
src="https://github.com/user-attachments/assets/aba11769-02be-4905-97e1-e24485e24cd0"
/>

4.Ask a natural language query in chat.
<img width="2550" height="1134" alt="query"
src="https://github.com/user-attachments/assets/26a910a6-e503-4ac7-b66a-f5754bbb0e91"
/>

common/settings.py

@@ -79,6 +79,7 @@ FEISHU_OAUTH = None
 OAUTH_CONFIG = None
 DOC_ENGINE = os.getenv('DOC_ENGINE', 'elasticsearch')
 DOC_ENGINE_INFINITY = (DOC_ENGINE.lower() == "infinity")
+DOC_ENGINE_OCEANBASE = (DOC_ENGINE.lower() == "oceanbase")
 
 
 docStoreConn = None
@@ -241,9 +242,10 @@ def init_settings():
     FEISHU_OAUTH = get_base_config("oauth", {}).get("feishu")
     OAUTH_CONFIG = get_base_config("oauth", {})
 
-    global DOC_ENGINE, DOC_ENGINE_INFINITY, docStoreConn, ES, OB, OS, INFINITY
+    global DOC_ENGINE, DOC_ENGINE_INFINITY, DOC_ENGINE_OCEANBASE, docStoreConn, ES, OB, OS, INFINITY
     DOC_ENGINE = os.environ.get("DOC_ENGINE", "elasticsearch")
     DOC_ENGINE_INFINITY = (DOC_ENGINE.lower() == "infinity")
+    DOC_ENGINE_OCEANBASE = (DOC_ENGINE.lower() == "oceanbase")
     lower_case_doc_engine = DOC_ENGINE.lower()
     if lower_case_doc_engine == "elasticsearch":
         ES = get_base_config("es", {})