Refactor image, Java sourcing, and add entrypoint

- Moved to debian-slim base image to minimize size
- Transitioned to Adoptium APT repos for flexibility in Java versions
- Added an entrypoint script that configures EULA and server settings
- Run server in resumable screen for console access in the container

entrypoint.sh

@@ -0,0 +1,59 @@
+#!/bin/bash
+
+# Enable debug mode
+DEBUG="${DEBUG:-false}"
+if [ "$DEBUG" = "true" ]; then
+  echo "[DEBUG] Running entrypoint script at $(which entrypoint.sh)"
+  sleep 0.2
+  set -ux
+fi
+
+# Settings
+FILE="${FILE:-/app/server.properties}"
+EULAFILE="${EULAFILE:-/app/eula.txt}"
+PREFIX="${PREFIX:-SETTINGS_}"
+JVM_OPTS="${JVM_OPTS:--Xms1G -Xmx2G}"
+
+# Set EULA
+sed -i.bak "s/^eula=.*\$/eula=${EULA:-false}/" "$EULAFILE"
+diff --unified=1 "${EULAFILE}.bak" "$EULAFILE"
+rm "${EULAFILE}.bak"
+
+# Update server.properties using env
+while IFS='=' read -r ENVVAR VALUE ; do
+  if echo "$ENVVAR" | grep -q "^${PREFIX}.*$"; then
+    KEY="${ENVVAR#"$PREFIX"}"
+    if ! grep -q "^${KEY}=" "$FILE"; then
+      echo "[WARN]: \"$KEY\" does not exist in $FILE and was not updated"
+    else
+      [ "$DEBUG" = "true" ] && echo "[DEBUG] Updating \"$KEY\" to \"$VALUE\""
+      sed -i.bak "s/^${KEY}=.*/${KEY}=${VALUE}/" "$FILE"
+      diff --unified=1 "${FILE}.bak" "$FILE"
+      rm "${FILE}.bak"
+    fi
+  else
+    [ "$DEBUG" = "true" ] && \
+      echo "[DEBUG] \"$ENVVAR\" doesn't have the prefix \"$PREFIX\""
+  fi
+done < <(env)
+
+# Show server.properties in DEBUG mode
+if [ "$DEBUG" = "true" ]; then
+  echo "[DEBUG] Showing ${FILE}:"
+  cat "$FILE"
+fi
+
+# Pre-create the screen log
+touch screenlog.0
+
+# Run server in screen (without attaching)
+/usr/bin/screen -dmS minecraft -L \
+  bash -c "
+    sleep 0.5
+    [ $DEBUG = true ] && echo '[DEBUG] Starting server'
+    /usr/bin/java $JVM_OPTS -jar server.jar --nogui
+  "
+
+# Tail screen log to container stdout
+[ "$DEBUG" = "true" ] && echo "[DEBUG] Tailing screenlog.0"
+tail -f screenlog.0