fix: 趋势页恢复体重 + 图标换Material Icons + VLM禁用思考模式

- 健康概览页恢复体重指标的标签/单位/加载/筛选/录入
- 历史记录图标从emoji改为Material Icons
- VLM请求显式设置enable_thinking=false，禁用混合思考加速识图

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

@@ -119,6 +119,7 @@ public sealed class VisionClient(HttpClient http, IConfiguration config)
         {
             Model = _model, Messages = messages, MaxTokens = maxTokens, Stream = false,
             Temperature = 0.1f, VlHighResolutionImages = true,
+            EnableThinking = false,
         };
 
         var json = JsonSerializer.Serialize(request, _jsonOptions);

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

@@ -13,6 +13,9 @@ public sealed class ChatCompletionRequest
 
     [System.Text.Json.Serialization.JsonPropertyName("vl_high_resolution_images")]
     public bool VlHighResolutionImages { get; set; }
+
+    [System.Text.Json.Serialization.JsonPropertyName("enable_thinking")]
+    public bool? EnableThinking { get; set; }
 }
 
 public sealed class ChatMessage