regtest: add Fulcrum (Electrum/WS) with ZMQ push for Hal realtimeregtest-fulcrum

Adds a regtest Fulcrum service matching what prod runs, replacing the old
electrs + ews bridge as the data/realtime backend for the Hal browser wallet.
It connects to `bc` and gets instant block/mempool notifications over bitcoind's
ZMQ (hashblock/hashtx), serving them to the browser over an Electrum WebSocket
(:50003) — sub-second deposit + confirmation updates on regtest.

- docker/fulcrum.Dockerfile: Fulcrum on ghcr.io/coinos/base (shares layers with
  the rest of the stack instead of a separate image tree).
- compose.fulcrum.yml: opt-in overlay (`-f compose.fulcrum.yml up -d`), config +
  datadir under the gitignored data/ (seeded from sampledata by setup.sh).
- sampledata/fulcrum/fulcrum.conf: regtest config pointed at `bc`, ZMQ enabled.
- sampledata/bitcoin/bitcoin.conf: add zmqpubhashblock/hashtx (18508/18509) so
  Fulcrum can subscribe for instant notifications.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

1 files changed, 13 insertions, 0 deletions

diff --git a/docker/fulcrum.Dockerfile b/docker/fulcrum.Dockerfile
new file mode 100644
index 00000000..3f80b95a
--- /dev/null
+++ b/docker/fulcrum.Dockerfile
@@ -0,0 +1,13 @@
+# Fulcrum on the coinos base image. The static upstream release binary is
+# self-contained, so we just drop it onto ghcr.io/coinos/base — the rest of the
+# coinos stack already uses that base, so this shares layers instead of pulling
+# a separate Fulcrum image tree. Matches the prod Fulcrum version.
+FROM ghcr.io/coinos/base
+USER root
+ARG VERSION=2.1.1
+ADD https://github.com/cculianu/Fulcrum/releases/download/v${VERSION}/Fulcrum-${VERSION}-x86_64-linux.tar.gz /tmp/f.tar.gz
+RUN tar xzf /tmp/f.tar.gz -C /usr/local/bin --strip-components=1 \
+      Fulcrum-${VERSION}-x86_64-linux/Fulcrum Fulcrum-${VERSION}-x86_64-linux/FulcrumAdmin \
+    && rm /tmp/f.tar.gz && mkdir -p /etc/fulcrum /data
+ENTRYPOINT ["Fulcrum"]
+CMD ["/etc/fulcrum/fulcrum.conf"]