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>

contrib/Dockerfile

@@ -1,52 +0,0 @@
-# ElectrumX for Bitcoin, with RocksDB
-# This is a simple ~minimal example Dockerfile.
-#
-# Build: docker build --pull -t electrumx .
-#        podman build --pull  -t electrumx .
-# Run:   docker run -d --net=host -v ~/electrumx-db:/var/lib/electrumx -e DAEMON_URL="http://youruser:yourpass@localhost:8332" -e REPORT_SERVICES=tcp://example.com:50001 electrumx
-#        podman run -d --net=host -v ~/electrumx-db:/var/lib/electrumx -e DAEMON_URL="http://youruser:yourpass@localhost:8332" -e REPORT_SERVICES=tcp://example.com:50001 electrumx
-# Stop:  docker stop CONTAINER_ID
-#        podman stop CONTAINER_ID
-
-FROM python:3.14-trixie AS builder
-
-WORKDIR /usr/src/app
-
-# Install the libs needed by rocksdb (including development headers)
-RUN apt-get update \
-    && apt-get -y --no-install-recommends install \
-        build-essential \
-        git \
-        librocksdb-dev \
-        pkg-config \
-    && rm -rf /var/lib/apt/lists/*
-
-# Install ElectrumX
-ARG ELECTRUMX_VERSION=2.0.0
-#ARG ELECTRUMX_VERSION=b8f6e227f251fe5cba96b940ffaa094439636417
-RUN python -m venv venv \
-    && venv/bin/pip install --no-cache-dir \
-        "e_x[rocksdb] @ git+https://github.com/spesmilo/electrumx.git@${ELECTRUMX_VERSION}"
-
-
-FROM python:3.14-slim-trixie
-
-# Install the libs needed by rocksdb (no development headers or statics)
-RUN apt-get update && apt-get -y --no-install-recommends install librocksdb9.10 && rm -rf /var/lib/apt/lists/*
-
-ENV SERVICES="tcp://:50001"
-ENV COIN=Bitcoin
-ENV DB_DIRECTORY=/var/lib/electrumx
-ENV DAEMON_URL="http://username:password@hostname:port/"
-ENV ALLOW_ROOT=true
-ENV DB_ENGINE=rocksdb
-#ENV CACHE_MB=2000
-
-WORKDIR /usr/src/app
-COPY --from=builder /usr/src/app .
-
-VOLUME /var/lib/electrumx
-
-RUN mkdir -p "$DB_DIRECTORY"
-
-CMD ["/usr/src/app/venv/bin/python", "/usr/src/app/venv/bin/electrumx_server"]