engine.io (via socket.io) depends on zishang520/webtransport-go v0.9.1,
which is pinned to old quic-go internals and breaks against newer
quic-go releases, blocking dependabot's quic-go bump (#74).
Add internal/compat/zishang520-webtransport-go, a shim module that
preserves the zishang520/webtransport-go API shape while delegating to
the maintained quic-go/webtransport-go v0.10.0, wired in with a go.mod
replace directive. The Dockerfiles COPY the shim before go mod download
so the replace resolves in container builds.
Also bumps the Go toolchain to 1.26.4 and golang.org/x/crypto, x/sys,
and x/image.
Closes#74.
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
