Go: implement Rerank in Aliyun driver (#14676)

### What problem does this PR solve?

The Aliyun Go driver has a stub `Rerank` method that always returns
`"Aliyun, Rerank not implemented"`. DashScope exposes an
OpenAI-compatible rerank endpoint (`compatible-mode/v1/rerank`) and
hosts dedicated bilingual rerankers (`gte-rerank-v2`, `gte-rerank`) that
are a natural pairing with the embedding models already in
`aliyun.json`. Without this, Aliyun users cannot use reranking within
RAGFlow.

Closes #14675

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

conf/models/aliyun.json

@@ -8,6 +8,7 @@
   "url_suffix": {
     "chat": "compatible-mode/v1/chat/completions",
     "embedding": "compatible-mode/v1/embeddings",
+    "rerank": "compatible-api/v1/reranks",
     "models": "api/v1/deployments/models"
   },
   "models": [
@@ -31,6 +32,13 @@
       "model_types": [
         "embedding"
       ]
+    },
+    {
+      "name": "qwen3-rerank",
+      "max_tokens": 8192,
+      "model_types": [
+        "rerank"
+      ]
     }
   ],
   "features": {

internal/entity/models/aliyun.go

@@ -458,9 +458,108 @@ func (z *AliyunModel) Encode(modelName *string, texts []string, apiConfig *APICo
 	return embeddings, nil
 }
 
-// Rerank calculates similarity scores between query and texts
+type aliyunRerankRequest struct {
+	Model           string   `json:"model"`
+	Query           string   `json:"query"`
+	Documents       []string `json:"documents"`
+	TopN            int      `json:"top_n"`
+	ReturnDocuments bool     `json:"return_documents"`
+}
+
+type aliyunRerankResponse struct {
+	Results []struct {
+		Index          int     `json:"index"`
+		RelevanceScore float64 `json:"relevance_score"`
+	} `json:"results"`
+}
+
 func (z *AliyunModel) Rerank(modelName *string, query string, texts []string, apiConfig *APIConfig) ([]float64, error) {
-	return nil, fmt.Errorf("%s, Rerank not implemented", z.Name())
+	if len(texts) == 0 {
+		return []float64{}, nil
+	}
+	if apiConfig == nil || apiConfig.ApiKey == nil || *apiConfig.ApiKey == "" {
+		return nil, fmt.Errorf("api key is required")
+	}
+	if modelName == nil || *modelName == "" {
+		return nil, fmt.Errorf("model name is required")
+	}
+
+	region := "default"
+	if apiConfig.Region != nil && *apiConfig.Region != "" {
+		region = *apiConfig.Region
+	}
+
+	baseURL := z.BaseURL["default"]
+	if region != "default" {
+		if regional, ok := z.BaseURL[region]; ok && regional != "" {
+			baseURL = regional
+		}
+	}
+	if baseURL == "" {
+		return nil, fmt.Errorf("aliyun: no base URL configured for default region")
+	}
+
+	url := fmt.Sprintf("%s/%s", strings.TrimSuffix(baseURL, "/"), z.URLSuffix.Rerank)
+
+	reqBody := aliyunRerankRequest{
+		Model:           *modelName,
+		Query:           query,
+		Documents:       texts,
+		TopN:            len(texts),
+		ReturnDocuments: false,
+	}
+
+	jsonData, err := json.Marshal(reqBody)
+	if err != nil {
+		return nil, fmt.Errorf("failed to marshal request: %w", err)
+	}
+
+	req, err := http.NewRequest("POST", url, bytes.NewBuffer(jsonData))
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", *apiConfig.ApiKey))
+
+	resp, err := z.httpClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("failed to send request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read response: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("Aliyun rerank API error: %s, body: %s", resp.Status, string(body))
+	}
+
+	var rerankResp aliyunRerankResponse
+	if err = json.Unmarshal(body, &rerankResp); err != nil {
+		return nil, fmt.Errorf("failed to parse response: %w", err)
+	}
+
+	scores := make([]float64, len(texts))
+	seen := make([]bool, len(texts))
+	for _, r := range rerankResp.Results {
+		if r.Index < 0 || r.Index >= len(texts) {
+			return nil, fmt.Errorf("aliyun rerank: result index %d out of range for %d documents", r.Index, len(texts))
+		}
+		if seen[r.Index] {
+			return nil, fmt.Errorf("aliyun rerank: duplicate result index %d", r.Index)
+		}
+		scores[r.Index] = r.RelevanceScore
+		seen[r.Index] = true
+	}
+
+	if len(rerankResp.Results) != len(texts) {
+		return nil, fmt.Errorf("aliyun rerank: expected %d results, got %d", len(texts), len(rerankResp.Results))
+	}
+
+	return scores, nil
 }
 
 type AliyunModelItem struct {