Add project files.

Gateway/ProviderClients/GoogleProviderClient.cs

@@ -0,0 +1,60 @@
+using System.Net.Http.Json;
+using System.Text.Json;
+using Gateway.Models;
+
+namespace Gateway.ProviderClients;
+
+public sealed class GoogleProviderClient
+{
+    private readonly HttpClient _http;
+    private readonly IConfiguration _config;
+    private readonly ILogger<GoogleProviderClient> _logger;
+
+    public GoogleProviderClient(HttpClient http, IConfiguration config, ILogger<GoogleProviderClient> logger)
+    {
+        _http = http;
+        _config = config;
+        _logger = logger;
+    }
+
+    private string GetInternalKey()
+        => _config["Provider:Google:InternalKey"] 
+           ?? Environment.GetEnvironmentVariable("GOOGLE_INTERNAL_KEY") 
+           ?? "";
+
+    public async Task<(int status, ProviderResponse body)> ExecuteAsync(ProviderRequest req, CancellationToken ct)
+    {
+        var key = GetInternalKey();
+        if (string.IsNullOrWhiteSpace(key))
+            return (500, new ProviderResponse { Ok = false, RequestId = req.RequestId, Error = new ProviderError { Code = "CONFIG", Message = "Missing Google internal key" } });
+
+        using var msg = new HttpRequestMessage(HttpMethod.Post, "internal/execute");
+        msg.Headers.Add("X-Internal-Key", key);
+        msg.Content = JsonContent.Create(req, options: new JsonSerializerOptions(JsonSerializerDefaults.Web));
+
+        var res = await _http.SendAsync(msg, ct);
+
+        ProviderResponse? body = null;
+        try
+        {
+            body = await res.Content.ReadFromJsonAsync<ProviderResponse>(cancellationToken: ct);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogWarning(ex, "Failed to parse provider response as JSON");
+        }
+
+        body ??= new ProviderResponse
+        {
+            Ok = res.IsSuccessStatusCode,
+            RequestId = req.RequestId,
+            Error = res.IsSuccessStatusCode ? null : new ProviderError { Code = "PROVIDER", Message = "Non-JSON error from provider" }
+        };
+
+        // If provider returned a 4xx/5xx but body says Ok=true, normalize
+        if (!res.IsSuccessStatusCode && body.Ok)
+            body.Ok = false;
+
+        return ((int)res.StatusCode, body);
+    }
+}