feat(api): add account workspaces and signed content events

server/tests/WebDrop.Api.Tests/ServerFixture.cs

@@ -117,7 +117,8 @@ public sealed class ServerFixture : IAsyncLifetime, IAsyncDisposable
             ["write_hash"] = B64(TokenHash.Compute(ch.WriteToken)),
         };
         if (mode == ChannelMode.Enc) body["read_hash"] = B64(TokenHash.Compute(ch.ReadToken));
-        if (settings is not null) body["settings"] = settings;
+        // General transport tests explicitly use open spaces; creation defaults have separate coverage.
+        body["settings"] = settings ?? new { name = "Test space", seats = 2, join_policy = "open", allow_guests = true };
 
         using var req = Req(HttpMethod.Post, "/api/v1/channels", ch.Owner, JsonBody(body));
         if (capToken is not null) req.Headers.Add("X-WD-Cap", capToken);