### What problem does this PR solve?
This PR adds non-streaming chat support for the Jina Go model provider.
The Jina provider was added with embedding, rerank, model listing, and
connection checking, but `ChatWithMessages` still returned a
not-implemented error even though Jina exposes an OpenAI-compatible
`/v1/chat/completions` endpoint.
Closes#14933
**The following functionalities are now supported:**
### **Jina:**
- [x] Chat
- [ ] Stream Chat
- [x] Embedding
- [x] Rerank
- [x] Model listing
- [x] Provider connection checking
- [ ] Balance
### **Implementation details:**
- Implements `JinaModel.ChatWithMessages`
- Sends `Authorization: Bearer <api-key>` and JSON chat completion
requests
- Validates API key, model name, messages, and configured region before
making requests
- Forwards supported chat config fields: `max_tokens`, `temperature`,
`top_p`, and `stop`
- Parses the first chat completion choice into `ChatResponse.Answer`
- Adds `jina-ai/jina-vlm` as a chat-capable model in
`conf/models/jina.json`
- Adds focused unit tests for request construction, auth, response
parsing, validation errors, provider errors, and region handling
**Verification:**
```plaintext
docker run --rm -v $PWD:/repo -w /repo golang:1.25 sh -c '/usr/local/go/bin/gofmt -w internal/entity/models/jina.go internal/entity/models/jina_test.go && /usr/local/go/bin/go test -vet=off ./internal/entity/models -run TestJina -count=1'
ok ragflow/internal/entity/models 0.037s
```
Note: `go test ./internal/entity/models -run TestJina -count=1`
currently hits unrelated existing vet findings in other provider files,
so the focused Jina tests were run with `-vet=off`.
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
---------
Co-authored-by: Jin Hai <haijin.chn@gmail.com>
### What problem does this PR solve?
This PR completes the Jina provider
**The following functionalities are now supported:**
**Jina:**
- [ ] Chat / Stream Chat (Not available for now: [(Jina chat API
docs)](https://api.jina.ai/docs#/Search%20Foundation%20Models/chat_completions_v1_chat_completions_post))
- [x] Embedding
- [x] Rerank
- [x] Model listing
- [x] Provider connection checking
- [ ] ~~Balance~~
**Verified examples from the CLI:**
```plaintext
RAGFlow(user)> embed text 'walkerwhat' 'jumperwho' with 'jina-embeddings-v2-base-en@test@jina' dimension 16
+-----------+-------+
| dimension | index |
+-----------+-------+
| 768 | 0 |
| 768 | 1 |
+-----------+-------+
RAGFlow(user)> rerank query 'what is rag' document 'rag is retrieval augment generation' 'rag need llm' 'famous rag project includes ragflow' with 'jina-reranker-v2-base-multilingual@test@jina' top 3;
+-------+-----------------+
| index | relevance_score |
+-------+-----------------+
| 0 | 0.74316794 |
| 2 | 0.18713269 |
| 1 | 0.15817434 |
+-------+-----------------+
RAGFlow(user)> list supported models from 'jina' 'test'
+---------------------------------------------+
| model_name |
+---------------------------------------------+
| Jina AI: Jina VLM |
| Jina AI: Jina Reranker v3 |
| Jina AI: Jina Code Embeddings 0.5b |
| Jina AI: Jina Code Embeddings 1.5b |
| Jina AI: Jina Embeddings v4 |
| Jina AI: Jina Reranker M0 |
| Jina AI: ReaderLM v2 |
| Jina AI: Jina Clip v2 |
| Jina AI: Jina Embeddings v3 |
| Jina AI: Jina Colbert v2 |
| Jina AI: Reader LM 0.5b |
| Jina AI: Reader LM 1.5b |
| Jina AI: Jina Reranker v2 Base Multilingual |
| Jina AI: Jina Clip v1 |
| Jina AI: Jina Reranker v1 Tiny EN |
| Jina AI: Jina Reranker v1 Turbo EN |
| Jina AI: Jina Reranker v1 Base EN |
| Jina AI: Jina Colbert v1 EN |
| Jina AI: Jina Embeddings v2 Base ES |
| Jina AI: Jina Embeddings v2 Base Code |
| Jina AI: Jina Embeddings v2 Base DE |
| Jina AI: Jina Embeddings v2 Base ZH |
| Jina AI: Jina Embeddings v2 Base EN |
| Jina AI: Jina Embedding B EN v1 |
| Jina AI: Jina Embeddings v5 Text Small |
| Jina AI: Jina Embeddings v5 Omni Small |
| Jina AI: Jina Embeddings v5 Omni Nano |
| Jina AI: Jina Embeddings v5 Text Nano |
+---------------------------------------------+
RAGFlow(user)> check instance 'test' from 'jina'
SUCCESS
```
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
