Fix Dockerfile base images and add docker-compose

Switch to available base images (temurin-21) since clojure:openjdk-25
and azul/zulu-openjdk-alpine:25 no longer exist. Add docker-compose.yml
for single-command app deployment.

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

Dockerfile

@@ -8,7 +8,7 @@ COPY src/ src/
 COPY tailwind.config.js ./
 RUN npm run css:build
 
-FROM clojure:openjdk-25 AS build
+FROM clojure:temurin-21-tools-deps-alpine AS build
 
 WORKDIR /build
 COPY deps.edn build.clj ./
@@ -17,7 +17,7 @@ COPY . .
 COPY --from=css /build/resources/public/css/output.css resources/public/css/output.css
 RUN clj -T:build all
 
-FROM azul/zulu-openjdk-alpine:25
+FROM eclipse-temurin:21-jre-alpine
 
 COPY --from=build /build/target/btcprice-standalone.jar /btcprice/btcprice-standalone.jar