VolcEngine SDK V3 adaptation (#2082)

1) Configuration interface update
2) Back-end adaptation API update
Note: The official no longer supports the Skylark1/2 series, and all
have been switched to the Doubao series


![image](https://github.com/user-attachments/assets/f6fd8782-0cdf-4c0b-ac8f-9eb130f667a5)

### What problem does this PR solve?

_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._

### Type of change

- [x] 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):

Co-authored-by: 海贼宅 <stu_xyx@163.com>

api/apps/llm_app.py

@@ -113,13 +113,10 @@ def add_llm():
 
     if factory == "VolcEngine":
         # For VolcEngine, due to its special authentication method
-        # Assemble volc_ak, volc_sk, endpoint_id into api_key
-        temp = list(ast.literal_eval(req["llm_name"]).items())[0]
-        llm_name = temp[0]
-        endpoint_id = temp[1]
-        api_key = '{' + f'"volc_ak": "{req.get("volc_ak", "")}", ' \
-                        f'"volc_sk": "{req.get("volc_sk", "")}", ' \
-                        f'"ep_id": "{endpoint_id}", ' + '}'
+        # Assemble ark_api_key endpoint_id into api_key
+        llm_name = req["llm_name"]
+        api_key = '{' + f'"ark_api_key": "{req.get("ark_api_key", "")}", ' \
+                        f'"ep_id": "{req.get("endpoint_id", "")}", ' + '}'
     elif factory == "Tencent Hunyuan":
         api_key = '{' + f'"hunyuan_sid": "{req.get("hunyuan_sid", "")}", ' \
                         f'"hunyuan_sk": "{req.get("hunyuan_sk", "")}"' + '}'