Dockerize Nebula (#31)

* feat: introduce docker and compose

* feat: add public host/port env var

Added `NEBULA_PUBLIC_HOST` and `NEBULA_PUBLIC_PORT` environment variables. Will override config values.

* chore: update compose manifest

Add `NEBULA_PUBLIC_PORT` environment variable for serverlist.

Dockerfile

@@ -0,0 +1,29 @@
+# Build Nebula.jar
+FROM eclipse-temurin:21-jdk-alpine-3.23 AS build
+WORKDIR /build
+RUN apk add --no-cache gradle
+COPY . .
+RUN gradle jar
+
+# Grab latest resources
+FROM alpine:3.23 AS resources
+WORKDIR /build
+RUN apk add --no-cache git wget
+RUN git clone --depth=1 https://github.com/Hiro420/StellaSoraData
+RUN wget https://nova-static.stellasora.global/meta/and.html
+RUN wget https://nova-static.stellasora.global/meta/win.html
+
+# Final image
+# Resources are included in the image for the sake of convenience.
+FROM eclipse-temurin:25-alpine-3.23
+WORKDIR /app
+EXPOSE 80
+RUN apk add --no-cache curl
+HEALTHCHECK --interval=5s --timeout=15s --retries=3 --start-period=10s CMD [ "curl", "http://127.0.0.1:80" ]
+RUN mkdir /app/resources && mkdir /app/web && mkdir /app/web/meta
+COPY --from=build /build/Nebula.jar .
+COPY --from=resources /build/StellaSoraData/EN/bin/ /app/resources/bin/
+COPY --from=resources /build/StellaSoraData/EN/language/ /app/resources/language/
+COPY --from=resources /build/and.html /app/web/meta/and.html
+COPY --from=resources /build/win.html /app/web/meta/win.html
+CMD [ "java", "-jar", "/app/Nebula.jar", "-nohandbook" ]