fix(pool): update Dockerfile and config for Lethean testnet

- Dockerfile: node:8 → node:20, modern build chain
- Config: ports 5555/7777/8888, Redis auth, testnet difficulty
- Remove cryptonight-hashing dependency (ProgPoWZ via zano-node-util)

Co-Authored-By: Charon <charon@lethean.io>

Dockerfile

@@ -1,23 +1,28 @@
-# Why node:8 and not node:10? Because (a) v8 is LTS, so more likely to be stable, and (b) "npm update" on node:10 breaks on Docker on Linux (but not on OSX, oddly)
-FROM node:8-slim
+FROM node:20-bookworm-slim AS builder
 
-RUN apt-get update \
-  && DEBIAN_FRONTEND=noninteractive apt-get install -y nodejs-legacy npm git libboost1.55-all libssl-dev \
-  && rm -rf /var/lib/apt/lists/* && \
-  chmod +x /wait-for-it.sh
+RUN apt-get update && \
+    DEBIAN_FRONTEND=noninteractive apt-get install -y \
+    git python3 make g++ cmake libboost-all-dev libssl-dev && \
+    rm -rf /var/lib/apt/lists/*
 
-ADD . /pool/
-WORKDIR /pool/
+WORKDIR /pool
 
-RUN npm update
+# Copy zano-node-util first (native dependency)
+COPY ../zano-node-util /zano-node-util
 
-RUN mkdir -p /config
+# Copy pool source
+COPY package.json .
+RUN npm install --ignore-scripts
 
-EXPOSE 8117
-EXPOSE 3333
-EXPOSE 5555
-EXPOSE 7777
+# Build native modules
+RUN cd node_modules/bignum && npx node-gyp rebuild || true
 
-VOLUME ["/config"]
+COPY . .
 
-CMD node init.js -config=/config/config.json
+FROM node:20-bookworm-slim
+WORKDIR /pool
+COPY --from=builder /pool /pool
+
+EXPOSE 2117 5555 7777 8888
+
+CMD ["node", "init.js"]