Add Dockerfile and docker-compose.yml to run next to the Palladium node

ElectrumX is built from this source tree with RocksDB and joins the external
'palladium' network of the node in palladiumcore/docker, reaching it as
palladiumd:2332. RPC credentials come from .env (ignored by git, see
.env.example). The Bitcoin-specific contrib/Dockerfile is removed.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,52 @@
+# plm-electrumx: ElectrumX server for Palladium, with RocksDB, built from this source tree.
+#
+#   docker compose up -d --build        (see docker-compose.yml and README.md)
+#
+# Runs on the "palladium" network of the node in palladiumcore/docker and reaches it as palladiumd:2332.
+
+FROM python:3.14-trixie AS builder
+
+WORKDIR /usr/src/app
+
+# the libs needed by rocksdb (including development headers)
+RUN apt-get update \
+    && apt-get -y --no-install-recommends install \
+        build-essential \
+        librocksdb-dev \
+        pkg-config \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY pyproject.toml README.md LICENCE MANIFEST.in ./
+COPY src ./src
+RUN python -m venv venv \
+    && venv/bin/pip install --no-cache-dir ".[rocksdb]"
+
+
+FROM python:3.14-slim-trixie
+
+# the libs needed by rocksdb (no development headers or statics)
+RUN apt-get update && apt-get -y --no-install-recommends install librocksdb9.10 && rm -rf /var/lib/apt/lists/*
+
+ENV COIN=Palladium
+ENV NET=mainnet
+ENV DB_ENGINE=rocksdb
+ENV DB_DIRECTORY=/var/lib/electrumx
+ENV SERVICES="tcp://:50001"
+# set at run time, see docker-compose.yml:
+#ENV DAEMON_URL="http://user:password@palladiumd:2332/"
+#ENV CACHE_MB=2000
+#ENV REPORT_SERVICES=tcp://example.com:50001
+
+WORKDIR /usr/src/app
+COPY --from=builder /usr/src/app/venv ./venv
+
+# the data directory is created here so that an empty volume is owned by the electrumx user
+RUN useradd --create-home --uid 1000 electrumx \
+    && mkdir -p "$DB_DIRECTORY" && chown electrumx:electrumx "$DB_DIRECTORY"
+USER electrumx
+VOLUME /var/lib/electrumx
+
+# 50001: Electrum protocol over TCP.
+EXPOSE 50001
+
+CMD ["/usr/src/app/venv/bin/electrumx_server"]