feat(quic-interop): scaffold quic-interop-runner endpoint module

Adds :quic-interop, a JVM-only module at quic/interop/ that implements
the quic-interop-runner Docker contract so we can drive matrix tests
against aioquic / quiche / picoquic / msquic / ngtcp2 / etc. as a
bug-finding harness.

Phase 0 supports only the `handshake` testcase; everything else returns
127 so the runner skips rather than fails. SSLKEYLOGFILE / QLOGDIR
plumbing is deferred to Phase 1.

https://claude.ai/code/session_01HcvfQq1ttPV9PkRoJb4nyT

quic/interop/Dockerfile

@@ -0,0 +1,16 @@
+# quic-interop-runner endpoint image for :quic.
+#
+# Build (from repo root):
+#   ./gradlew :quic-interop:installDist
+#   docker build -t amethyst-quic-interop -f quic/interop/Dockerfile .
+#
+# Or run `make build` inside quic/interop/.
+FROM martenseemann/quic-network-simulator-endpoint:latest
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends openjdk-21-jre-headless \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY quic/interop/build/install/quic-interop /opt/quic-interop
+COPY quic/interop/run_endpoint.sh /run_endpoint.sh
+RUN chmod +x /run_endpoint.sh /opt/quic-interop/bin/quic-interop