Add admin database download

RpgRoller.Tests/Api/CampaignApiTests.cs

@@ -1,3 +1,5 @@
+using System.Text;
+
 namespace RpgRoller.Tests;
 
 public sealed class CampaignApiTests : ApiTestBase
@@ -160,6 +162,40 @@ public sealed class CampaignApiTests : ApiTestBase
         Assert.Contains(usersAfterDelete, user => user.Id == gm.Id);
     }
 
+    [Fact]
+    public async Task AdminDatabaseDownload_RequiresAdminAndReturnsSqliteFile()
+    {
+        using var factory = CreateFactory();
+        using var anonymousClient = factory.CreateClient(new() { AllowAutoRedirect = false });
+        using var adminClient = factory.CreateClient(new() { AllowAutoRedirect = false });
+        using var memberClient = factory.CreateClient(new() { AllowAutoRedirect = false });
+
+        await RegisterAsync(adminClient, "admin-download", "Password123", "Admin Download");
+        await LoginAsync(adminClient, "admin-download", "Password123");
+
+        await RegisterAsync(memberClient, "member-download", "Password123", "Member Download");
+        await LoginAsync(memberClient, "member-download", "Password123");
+
+        var unauthorized = await anonymousClient.GetAsync("/api/admin/database");
+        Assert.Equal(HttpStatusCode.Unauthorized, unauthorized.StatusCode);
+
+        var forbidden = await memberClient.GetAsync("/api/admin/database");
+        Assert.Equal(HttpStatusCode.BadRequest, forbidden.StatusCode);
+
+        var response = await adminClient.GetAsync("/api/admin/database");
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.Equal("application/octet-stream", response.Content.Headers.ContentType?.MediaType);
+
+        var disposition = response.Content.Headers.ContentDisposition;
+        Assert.NotNull(disposition);
+        Assert.Equal("attachment", disposition.DispositionType);
+        Assert.EndsWith(".db", disposition.FileName?.Trim('"'), StringComparison.OrdinalIgnoreCase);
+
+        var bytes = await response.Content.ReadAsByteArrayAsync();
+        Assert.True(bytes.Length >= 16);
+        Assert.Equal("SQLite format 3\0", Encoding.ASCII.GetString(bytes, 0, 16));
+    }
+
     [Fact]
     public async Task CampaignOptionsEndpoint_ReturnsCampaignsBeyondVisibleCampaignList()
     {