feat: dreport-service + dreport-ffi + nuget packages

Extract orchestration (font registry + render pipeline) from the Axum
backend into a standalone dreport-service crate. Backend becomes a thin
HTTP adapter on top.

Add dreport-ffi (cdylib) exposing the service through a stable C ABI
with opaque handles, byte buffers, and thread-local error reporting.

Build Dreport.Service + Dreport.AspNetCore NuGet packages under
bindings/dotnet/, packing the host RID native binary via a generated
nuspec. justfile recipes (nuget-publish, nuget-publish-all) build,
pack, and push to the Gitea NuGet registry in one shot.

Test coverage: 47 Rust + 38 C# (xUnit + WebApplicationFactory).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

bindings/dotnet/tests/Dreport.AspNetCore.Tests/Dreport.AspNetCore.Tests.csproj

@@ -0,0 +1,22 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <IsPackable>false</IsPackable>
+    <LangVersion>latest</LangVersion>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.11.1" />
+    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="9.0.0" />
+    <PackageReference Include="xunit" Version="2.9.2" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\Dreport.AspNetCore\Dreport.AspNetCore.csproj" />
+  </ItemGroup>
+
+</Project>

bindings/dotnet/tests/Dreport.AspNetCore.Tests/EndpointTests.cs

@@ -0,0 +1,173 @@
+using System.Net;
+using System.Net.Http.Json;
+using System.Text;
+using System.Text.Json;
+using Dreport.AspNetCore;
+using Dreport.Service;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Mvc.Testing;
+using Microsoft.AspNetCore.TestHost;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Xunit;
+
+namespace Dreport.AspNetCore.Tests;
+
+/// <summary>
+/// Spins up an in-memory ASP.NET Core host for each test using TestServer
+/// directly, so we don't need a Program.cs entry point. Verifies the
+/// stock /api endpoints behave the same as the original Axum backend.
+/// </summary>
+public class EndpointTests
+{
+    private const string Template = """
+        {
+          "id": "aspnet-test",
+          "name": "AspNet Test",
+          "page": { "width": 210, "height": 297 },
+          "fonts": ["Noto Sans"],
+          "root": {
+            "id": "root",
+            "type": "container",
+            "position": { "type": "flow" },
+            "size": { "width": { "type": "auto" }, "height": { "type": "auto" } },
+            "direction": "column",
+            "gap": 5,
+            "padding": { "top": 15, "right": 15, "bottom": 15, "left": 15 },
+            "align": "stretch",
+            "justify": "start",
+            "style": {},
+            "children": [
+              {
+                "id": "title",
+                "type": "static_text",
+                "position": { "type": "flow" },
+                "size": { "width": { "type": "auto" }, "height": { "type": "auto" } },
+                "style": { "fontSize": 14, "fontWeight": "bold" },
+                "content": "Hello"
+              }
+            ]
+          }
+        }
+        """;
+
+    private static HttpClient Build(string prefix = "/api")
+    {
+        var builder = new WebHostBuilder()
+            .ConfigureServices(s => s.AddRouting().AddDreport())
+            .Configure(app =>
+            {
+                app.UseRouting();
+                app.UseEndpoints(e => e.MapDreportEndpoints(prefix));
+            });
+        var server = new TestServer(builder);
+        return server.CreateClient();
+    }
+
+    [Fact]
+    public async Task Health_Returns_Ok()
+    {
+        var client = Build();
+        var resp = await client.GetAsync("/api/health");
+        Assert.Equal(HttpStatusCode.OK, resp.StatusCode);
+        var json = await resp.Content.ReadFromJsonAsync<JsonElement>();
+        Assert.Equal("ok", json.GetProperty("status").GetString());
+    }
+
+    [Fact]
+    public async Task Render_ReturnsPdf()
+    {
+        var client = Build();
+        var payload = new { template = JsonDocument.Parse(Template).RootElement, data = new { } };
+        var resp = await client.PostAsJsonAsync("/api/render", payload);
+        Assert.Equal(HttpStatusCode.OK, resp.StatusCode);
+        Assert.Equal("application/pdf", resp.Content.Headers.ContentType?.MediaType);
+        var bytes = await resp.Content.ReadAsByteArrayAsync();
+        Assert.True(bytes.Length > 100);
+        Assert.Equal((byte)'%', bytes[0]);
+    }
+
+    [Fact]
+    public async Task Render_InvalidTemplate_Returns400()
+    {
+        var client = Build();
+        var payload = new { template = "not a template", data = new { } };
+        var resp = await client.PostAsJsonAsync("/api/render", payload);
+        Assert.Equal(HttpStatusCode.BadRequest, resp.StatusCode);
+    }
+
+    [Fact]
+    public async Task Layout_ReturnsJson()
+    {
+        var client = Build();
+        var payload = new { template = JsonDocument.Parse(Template).RootElement, data = new { } };
+        var resp = await client.PostAsJsonAsync("/api/layout", payload);
+        Assert.Equal(HttpStatusCode.OK, resp.StatusCode);
+        var json = await resp.Content.ReadFromJsonAsync<JsonElement>();
+        Assert.True(json.TryGetProperty("pages", out var pages));
+        Assert.Equal(JsonValueKind.Array, pages.ValueKind);
+    }
+
+    [Fact]
+    public async Task ListFonts_IncludesNotoSans()
+    {
+        var client = Build();
+        var resp = await client.GetAsync("/api/fonts");
+        Assert.Equal(HttpStatusCode.OK, resp.StatusCode);
+        var families = await resp.Content.ReadFromJsonAsync<JsonElement[]>();
+        Assert.NotNull(families);
+        Assert.Contains(families!, f => f.GetProperty("family").GetString()!.ToLowerInvariant().Contains("noto"));
+    }
+
+    [Fact]
+    public async Task GetFontBytes_KnownVariant_ReturnsTtf()
+    {
+        var client = Build();
+        var resp = await client.GetAsync("/api/fonts/Noto%20Sans/400/false");
+        Assert.Equal(HttpStatusCode.OK, resp.StatusCode);
+        Assert.Equal("font/ttf", resp.Content.Headers.ContentType?.MediaType);
+        var bytes = await resp.Content.ReadAsByteArrayAsync();
+        Assert.True(bytes.Length > 1000);
+    }
+
+    [Fact]
+    public async Task GetFontBytes_Unknown_Returns404()
+    {
+        var client = Build();
+        var resp = await client.GetAsync("/api/fonts/DoesNotExist/400/false");
+        Assert.Equal(HttpStatusCode.NotFound, resp.StatusCode);
+    }
+
+    [Fact]
+    public async Task CustomPrefix_RemapsAllEndpoints()
+    {
+        var client = Build("/dreport/api");
+        var resp = await client.GetAsync("/dreport/api/health");
+        Assert.Equal(HttpStatusCode.OK, resp.StatusCode);
+        var oldRoute = await client.GetAsync("/api/health");
+        Assert.Equal(HttpStatusCode.NotFound, oldRoute.StatusCode);
+    }
+
+    [Fact]
+    public async Task ManualUsage_LayoutEngine_FromDi()
+    {
+        // Sanity: AddDreport without MapDreportEndpoints still hands the engine
+        // out via DI so users can plug it into their own controllers.
+        var builder = new WebHostBuilder()
+            .ConfigureServices(s => s.AddRouting().AddDreport())
+            .Configure(app =>
+            {
+                app.UseRouting();
+                app.UseEndpoints(e => e.MapGet("/custom",
+                    (LayoutEngine engine) => Results.Json(new { count = engine.FontFamilyCount })));
+            });
+        using var server = new TestServer(builder);
+        var client = server.CreateClient();
+        var resp = await client.GetAsync("/custom");
+        Assert.Equal(HttpStatusCode.OK, resp.StatusCode);
+        var json = await resp.Content.ReadFromJsonAsync<JsonElement>();
+        Assert.True(json.GetProperty("count").GetInt32() >= 1);
+    }
+}