Add OpenAPI contract and generated frontend client

GameList.Tests/HelperTests.cs

@@ -40,6 +40,24 @@ public class HelperTests
         Assert.False(hasRewriteMethod);
     }
 
+    [Fact]
+    public async Task OpenApi_document_exposes_stable_operation_ids()
+    {
+        await using var factory = new TestWebApplicationFactory();
+        var client = factory.CreateClient();
+
+        var response = await client.GetAsync("/openapi/v1.json");
+        response.EnsureSuccessStatusCode();
+
+        var json = await response.Content.ReadFromJsonAsync<JsonElement>();
+        var paths = json.GetProperty("paths");
+
+        Assert.Equal("Login", paths.GetProperty("/api/auth/login").GetProperty("post").GetProperty("operationId").GetString());
+        Assert.Equal("GetState", paths.GetProperty("/api/state").GetProperty("get").GetProperty("operationId").GetString());
+        Assert.Equal("CreateSuggestion", paths.GetProperty("/api/suggestions").GetProperty("post").GetProperty("operationId").GetString());
+        Assert.Equal("DeletePlayer", paths.GetProperty("/api/admin/players/{playerId}").GetProperty("delete").GetProperty("operationId").GetString());
+    }
+
     [Fact]
     public async Task IsReachableImageAsync_rejects_redirect_and_accepts_image()
     {