refactor: modular init, add bedrock loader, dynamic java/healthcheck

- Split monolithic init into modular lib files under scripts/lib/
  (common.sh, java.sh, server.sh, loaders/{vanilla,paper,fabric,forge,neoforge}.sh)
- Add bedrock loader: downloads from Minecraft Services API,
  runs native binary with LD_LIBRARY_PATH, skips Java setup
- Add auto-detection for JAVA_VERSION from Mojang version manifest
  (MC 1.20.5+ -> temurin@21, 1.17-1.20.4 -> temurin@17,
   1.17 -> temurin@16, pre-1.17 -> temurin@8)
- Fix NEW_FORGE unbound variable when non-Forge loaders run
- Fix Fabric loader jq filter (-s slurp removed, null string check fixed)
- Fix Forge test detection (recursive find for forge-*-server.jar)
- Dynamic healthcheck: nc -z TCP 25565 for Java, nc -zu UDP 19132 for bedrock
- Add .gitea/workflows/build-dev.yml for dev branch CI builds
- Base image: debian:bookworm-slim (from ubuntu:noble)
- Add unzip, netcat-openbsd to Docker image
- Switch to shebangs, set -euo pipefail throughout

scripts/lib/loaders/paper.sh

@@ -0,0 +1,23 @@
+getPaper() {
+  SERVER_TYPE="Paper Minecraft"
+  if [[ ! -f server.jar ]]; then
+    if [[ -n "${PAPER_BUILD}" ]]; then
+      LATEST_BUILD="${PAPER_BUILD}"
+    else
+      LATEST_BUILD=$(curl -s https://api.papermc.io/v2/projects/${MC_LOADER}/versions/${MC_VERSION}/builds |
+        jq -r '[.builds[] | select(.channel | ascii_upcase == "STABLE")] | .[-1].build')
+    fi
+
+    if [ "$LATEST_BUILD" != "null" ]; then
+      JAR_NAME=${MC_LOADER}-${MC_VERSION}-${LATEST_BUILD}.jar
+      PAPERMC_URL="https://api.papermc.io/v2/projects/${MC_LOADER}/versions/${MC_VERSION}/builds/${LATEST_BUILD}/downloads/${JAR_NAME}"
+
+      curl -o server.jar "$PAPERMC_URL"
+      echo "Download completed"
+      echo "Minecraft Version: ${MC_VERSION}"
+      echo "Paper Version: ${LATEST_BUILD}"
+    else
+      echo "No stable build for version $MC_VERSION found :("
+    fi
+  fi
+}