fix: VLM识别修复 - 去System Message + 低温 + 精简提示词

backend/src/Health.Infrastructure/AI/ai_clients.cs

@@ -104,27 +104,23 @@ public sealed class VisionClient(HttpClient http, IConfiguration config)
         int maxTokens = 2048,
         CancellationToken ct = default)
     {
-        var messages = new List<ChatMessage>();
-        if (!string.IsNullOrEmpty(systemPrompt))
-            messages.Add(new ChatMessage { Role = "system", Content = systemPrompt });
-
         var contentParts = new List<object>();
         foreach (var url in imageUrls)
             contentParts.Add(new { type = "image_url", image_url = new { url } });
+        if (!string.IsNullOrEmpty(systemPrompt))
+            contentParts.Add(new { type = "text", text = systemPrompt });
         if (!string.IsNullOrEmpty(userText))
             contentParts.Add(new { type = "text", text = userText });
 
-        var userMessage = new ChatMessage
+        var messages = new List<ChatMessage>
         {
-            Role = "user",
-            Content = JsonSerializer.Serialize(contentParts, _jsonOptions)
+            new() { Role = "user", Content = JsonSerializer.Serialize(contentParts, _jsonOptions) }
         };
-        messages.Add(userMessage);
 
         var request = new ChatCompletionRequest
         {
             Model = _model, Messages = messages, MaxTokens = maxTokens, Stream = false,
-            Temperature = 0.7f, TopP = 0.8f,
+            Temperature = 0.1f, VlHighResolutionImages = true,
         };
 
         var json = JsonSerializer.Serialize(request, _jsonOptions);
@@ -136,7 +132,6 @@ public sealed class VisionClient(HttpClient http, IConfiguration config)
             throw new HttpRequestException($"VLM API {response.StatusCode}: {errorBody}");
         }
         var body = await response.Content.ReadAsStringAsync(ct);
-        Console.WriteLine($"[VLM RAW] Model={_model}, BodyLen={body.Length}, Body={body[..Math.Min(body.Length, 500)]}");
         return JsonSerializer.Deserialize<ChatCompletionResponse>(body, _jsonOptions)!;
     }
 }

backend/src/Health.Infrastructure/AI/open_ai_compatible_client.cs

@@ -167,6 +167,8 @@ public sealed class ChatCompletionRequest
     public float? TopP { get; set; }
     public List<ToolDefinition>? Tools { get; set; }
     public string? ToolChoice { get; set; }
+    [System.Text.Json.Serialization.JsonPropertyName("vl_high_resolution_images")]
+    public bool VlHighResolutionImages { get; set; }
 }
 
 public sealed class ChatMessage