Initial commit: btcdata — BTC data backend service

Split from btcprice monolith. Owns DB, migrations, Binance WebSocket,
Kraken OHLC pollers, and exposes a JSON API with SSE price stream.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,18 @@
+FROM clojure:temurin-21-tools-deps-alpine AS build
+
+WORKDIR /build
+COPY deps.edn build.clj ./
+RUN clj -Sforce -P
+COPY . .
+RUN clj -T:build all
+
+FROM eclipse-temurin:21-jre-alpine
+
+COPY --from=build /build/target/btcdata-standalone.jar /btcdata/btcdata-standalone.jar
+
+EXPOSE 4100
+ENV BTCDATA_PORT=4100
+ENV CORS_ORIGIN=http://localhost:4000
+ENV JDBC_URL=jdbc:postgresql://postgres:5432/btcprod
+
+CMD ["java", "-jar", "/btcdata/btcdata-standalone.jar"]