Add OFMX fetch helper

Author: ogrun

.gitignore

@@ -28,3 +28,5 @@ build/
 # OFMX data (downloaded/extracted)
 ofmx_lk.zip
 ofmx_lk/
+data/ofmx_lk.zip
+data/ofmx_lk/

scripts/fetch_ofmx.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+OFMX_URL="${OFMX_URL:-${1:-https://snapshots.openflightmaps.org/live/2513/ofmx/lkaa/latest/ofmx_lk.zip}}"
+OUT_DIR="${OUT_DIR:-data}"
+ZIP_PATH="${ZIP_PATH:-${OUT_DIR}/ofmx_lk.zip}"
+EXTRACT_DIR="${EXTRACT_DIR:-${OUT_DIR}/ofmx_lk}"
+
+if ! command -v unzip >/dev/null 2>&1; then
+  echo "Error: unzip is required." >&2
+  exit 1
+fi
+
+mkdir -p "${OUT_DIR}"
+
+if command -v curl >/dev/null 2>&1; then
+  curl -fL "${OFMX_URL}" -o "${ZIP_PATH}"
+elif command -v wget >/dev/null 2>&1; then
+  wget -O "${ZIP_PATH}" "${OFMX_URL}"
+else
+  echo "Error: curl or wget is required to download OFMX data." >&2
+  exit 1
+fi
+
+rm -rf "${EXTRACT_DIR}"
+unzip -q "${ZIP_PATH}" -d "${EXTRACT_DIR}"
+
+echo "Downloaded to ${ZIP_PATH}"
+echo "Extracted to ${EXTRACT_DIR}"