feat: 新增统一流式转发与统计能力，支持多API类型

新增统一流式处理机制，支持 Completions、Anthropic Messages、OpenAI Responses、Gemini GenerateContent 四种 API 的原封不动 SSE 转发
统一处理 token 用量统计、倍率计算、尊享包扣费与消息记录
新增统一发送接口 ai-chat/unified/send，支持从请求体自动解析模型 ID
提升多模型流式接入的一致性与扩展性

Yi.Abp.Net8/module/ai-hub/Yi.Framework.AiHub.Application/Services/Chat/AiChatService.cs

@@ -25,6 +25,7 @@ using Yi.Framework.AiHub.Domain.Entities.Model;
 using Yi.Framework.AiHub.Domain.Extensions;
 using Yi.Framework.AiHub.Domain.Managers;
 using Yi.Framework.AiHub.Domain.Shared.Consts;
+using System.Text.Json;
 using Yi.Framework.AiHub.Domain.Shared.Dtos;
 using Yi.Framework.AiHub.Domain.Shared.Dtos.OpenAi;
 using Yi.Framework.AiHub.Domain.Shared.Enums;
@@ -270,4 +271,89 @@ public class AiChatService : ApplicationService
         var data = await _agentStoreRepository.GetFirstAsync(x => x.SessionId == sessionId);
         return data?.Store;
     }
+
+    /// <summary>
+    /// 统一发送消息 - 支持4种API类型
+    /// </summary>
+    /// <param name="apiType">API类型枚举</param>
+    /// <param name="input">原始请求体JsonElement</param>
+    /// <param name="modelId">模型ID（Gemini格式需要从URL传入）</param>
+    /// <param name="sessionId">会话ID</param>
+    /// <param name="cancellationToken"></param>
+    [HttpPost("ai-chat/unified/send")]
+    public async Task PostUnifiedSendAsync(
+        [FromQuery] ModelApiTypeEnum apiType,
+        [FromBody] JsonElement input,
+        [FromQuery] string modelId,
+        [FromQuery] Guid? sessionId,
+        CancellationToken cancellationToken)
+    {
+        // 从请求体中提取模型ID（如果未从URL传入）
+        if (string.IsNullOrEmpty(modelId))
+        {
+            modelId = ExtractModelIdFromRequest(apiType, input);
+        }
+
+        // 除了免费模型，其他的模型都要校验
+        if (modelId != FreeModelId)
+        {
+            if (CurrentUser.IsAuthenticated)
+            {
+                await _aiBlacklistManager.VerifiyAiBlacklist(CurrentUser.GetId());
+                if (!CurrentUser.IsAiVip())
+                {
+                    throw new UserFriendlyException("该模型需要VIP用户才能使用，请购买VIP后重新登录重试");
+                }
+            }
+            else
+            {
+                throw new UserFriendlyException("未登录用户，只能使用未加速的DeepSeek-R1，请登录后重试");
+            }
+        }
+
+        // 如果是尊享包服务，需要校验是否尊享包足够
+        if (CurrentUser.IsAuthenticated)
+        {
+            var isPremium = await _modelManager.IsPremiumModelAsync(modelId);
+            if (isPremium)
+            {
+                var availableTokens = await _premiumPackageManager.GetAvailableTokensAsync(CurrentUser.GetId());
+                if (availableTokens <= 0)
+                {
+                    throw new UserFriendlyException("尊享token包用量不足，请先购买尊享token包");
+                }
+            }
+        }
+
+        // 调用统一流式处理
+        await _aiGateWayManager.UnifiedStreamForStatisticsAsync(
+            _httpContextAccessor.HttpContext!,
+            apiType,
+            input,
+            modelId,
+            CurrentUser.Id,
+            sessionId,
+            null,
+            CancellationToken.None);
+    }
+
+    /// <summary>
+    /// 从请求体中提取模型ID
+    /// </summary>
+    private string ExtractModelIdFromRequest(ModelApiTypeEnum apiType, JsonElement input)
+    {
+        try
+        {
+            if (input.TryGetProperty("model", out var modelProperty))
+            {
+                return modelProperty.GetString() ?? string.Empty;
+            }
+        }
+        catch
+        {
+            // 忽略解析错误
+        }
+
+        throw new UserFriendlyException("无法从请求中获取模型ID，请在URL参数中指定modelId");
+    }
 }