[Cloud] Knowledge Retrieval returns empty results in Workflow and Dataset API key endpoint returns 500

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### Dify version

1.17.0

### Cloud or Self Hosted

Cloud

### Steps to reproduce

1. Create a Knowledge Base in Dify Cloud.
2. Use "gemini-embedding-001" as the embedding model.
3. Upload documents and wait until they are available.
4. Open Retrieval Testing in the Knowledge Base.
5. Search for a term contained in the documents (for example, "はま寿司").
6. Confirm that Retrieval Testing successfully returns matching chunks.
7. Create a Workflow and add a Knowledge Retrieval node using the same Knowledge Base.
8. Set the Workflow input variable as the query for the Knowledge Retrieval node.
9. Run the Workflow with exactly the same query ("はま寿司").
10. The Knowledge Retrieval node completes successfully, but returns:

{"result":[]}

11. I also tried:
- Hybrid Search with reranking
- Weighted Score (Semantic 0.7 / Keyword 0.3)
- Top K = 10
- Score Threshold = OFF
- Creating a completely new Knowledge Retrieval node

The result is still empty.

Additionally, I enabled the Knowledge Service API, but no API key creation/management UI is displayed under API Access.

While logged in as the Workspace Owner, I tested:

GET /console/api/datasets/{dataset_id}/api-keys

Without X-Csrf-Token, it returns 401 as expected:
"CSRF token is missing or invalid."

With the valid X-Csrf-Token from the Dify Console session, the endpoint returns:

500 Internal Server Error
{"message":"Internal Server Error","code":"unknown","status":500}

### ✔️ Expected Behavior

The Knowledge Retrieval node in a Workflow should return the same relevant Knowledge chunks that are successfully returned by Retrieval Testing for the same Knowledge Base and query.

Also, when the Knowledge Service API is enabled, the Workspace Owner should be able to create or manage a Dataset/Knowledge API key so that the Knowledge retrieval API can be used.

### ❌ Actual Behavior

Retrieval Testing works correctly and returns relevant chunks, but the Knowledge Retrieval node in the Workflow always returns:

{"result":[]}

The node reports success, but no records are returned.

In addition, the Knowledge API Access area does not provide any API key creation/management UI, even for the Workspace Owner.

The internal dataset API-key GET endpoint returns HTTP 500 after valid CSRF authentication.

Start with the Workflow Knowledge Retrieval node and compare its behavior with Knowledge Base Retrieval Testing using the same query and embedding model. Then inspect GET /console/api/datasets/{dataset_id}/api-keys with and without the valid X-Csrf-Token. Done means matching chunks are returned in the workflow and Workspace Owners can manage API keys without a 500 response.

Written by the indexing model from the issue text.