chore: 全面规范化代码，遵循 CLAUDE.md 编码规范

- C# 文件命名改为 snake_case（28 个文件重命名）
- C# 类转换为主构造函数（8 个类）
- 空 catch 添加异常类型（2 处）
- 新建 GlobalUsings.cs（Health.Infrastructure、Health.WebApi）
- Flutter 移除 go_router，改用 Riverpod 路由栈
- Flutter 移除 flutter_secure_storage，改用 sqflite 持久化
- 修复 Flutter 构建路径（Flutter SDK 迁至 D 盘）
- 后端端口改为 0.0.0.0:5000，支持局域网访问

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

@@ -1,29 +1,20 @@
 using Microsoft.Extensions.Configuration;
 using System.Net.Http.Headers;
-using System.Text;
-using System.Text.Json;
 
 namespace Health.Infrastructure.AI;
 
 /// <summary>
 /// DeepSeek LLM 客户端（对话 + Tool Calling）
 /// </summary>
-public sealed class DeepSeekClient
+public sealed class DeepSeekClient(HttpClient http, IConfiguration config)
 {
-    private readonly HttpClient _http;
-    private readonly string _model;
-    private readonly JsonSerializerOptions _jsonOptions;
-
-    public DeepSeekClient(HttpClient http, IConfiguration config)
+    private readonly HttpClient _http = http;
+    private readonly string _model = config["DEEPSEEK_MODEL"] ?? "deepseek-chat";
+    private readonly JsonSerializerOptions _jsonOptions = new()
     {
-        _http = http;
-        _model = config["DEEPSEEK_MODEL"] ?? "deepseek-chat";
-        _jsonOptions = new()
-        {
-            PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
-            PropertyNameCaseInsensitive = true
-        };
-    }
+        PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
+        PropertyNameCaseInsensitive = true
+    };
 
     /// <summary>
     /// 流式 Chat Completions
@@ -96,22 +87,15 @@ public sealed class DeepSeekClient
 /// <summary>
 /// 千问 VL 视觉客户端（食物识别 + 报告解读）
 /// </summary>
-public sealed class QwenVisionClient
+public sealed class QwenVisionClient(HttpClient http, IConfiguration config)
 {
-    private readonly HttpClient _http;
-    private readonly string _model;
-    private readonly JsonSerializerOptions _jsonOptions;
-
-    public QwenVisionClient(HttpClient http, IConfiguration config)
+    private readonly HttpClient _http = http;
+    private readonly string _model = config["QWEN_VISION_MODEL"] ?? "qwen-vl-max";
+    private readonly JsonSerializerOptions _jsonOptions = new()
     {
-        _http = http;
-        _model = config["QWEN_VISION_MODEL"] ?? "qwen-vl-max";
-        _jsonOptions = new()
-        {
-            PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
-            PropertyNameCaseInsensitive = true
-        };
-    }
+        PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
+        PropertyNameCaseInsensitive = true
+    };
 
     public async Task<ChatCompletionResponse> VisionAsync(
         string systemPrompt,

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

@@ -1,33 +1,30 @@
 using System.Net.Http.Headers;
-using System.Text;
-using System.Text.Json;
 
 namespace Health.Infrastructure.AI;
 
 /// <summary>
 /// OpenAI 兼容协议 HTTP 客户端，统一调用 DeepSeek / 千问 VL
 /// </summary>
-public sealed class OpenAiCompatibleClient
+public sealed class OpenAiCompatibleClient(string baseUrl, string apiKey, string model)
 {
-    private readonly HttpClient _http;
-    private readonly string _model;
-    private readonly JsonSerializerOptions _jsonOptions;
-
-    public OpenAiCompatibleClient(string baseUrl, string apiKey, string model)
+    private readonly HttpClient _http = CreateHttpClient(baseUrl, apiKey);
+    private readonly string _model = model;
+    private readonly JsonSerializerOptions _jsonOptions = new()
     {
-        _http = new HttpClient
+        PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
+        PropertyNameCaseInsensitive = true
+    };
+
+    private static HttpClient CreateHttpClient(string baseUrl, string apiKey)
+    {
+        var client = new HttpClient
         {
             BaseAddress = new Uri(baseUrl.TrimEnd('/') + "/"),
             Timeout = TimeSpan.FromSeconds(60)
         };
-        _http.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", apiKey);
-        _http.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
-        _model = model;
-        _jsonOptions = new JsonSerializerOptions
-        {
-            PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
-            PropertyNameCaseInsensitive = true
-        };
+        client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", apiKey);
+        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
+        return client;
     }
 
     /// <summary>

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

@@ -1,5 +1,3 @@
-using Health.Domain.Enums;
-
 namespace Health.Infrastructure.AI;
 
 /// <summary>