Keep vanetza-idf in obu-firmware, so a plain clone builds the firmware

obu-firmware builds against the vanetza-idf C-ITS library, which until now
came from the colleague's microbu-esp32c5 tree beside the repository and was
not tracked here, so a clone of this repository could not build the firmware
it ships. The library alone is now part of obu-firmware, as
obu-firmware/external/vanetza-idf: their external/vanetza-idf at commit
cf4b99f, unchanged (9775 files; see its PROVENANCE.md). CMake takes it from
there by default; -DVANETZA_IDF_DIR still points the build elsewhere.

The rest of the colleague's tree (their own VAM firmware, PKI tooling,
station-link Python tools, the V2X2MAP bridge) stays out of this repository
and gitignored; nothing is pushed to their repository. NOTES.md, docs/06,
TODO.md and the pcap verifier's usage line point at the new location.

obu-firmware/external/vanetza-idf/tools/country-data/convert.py

@@ -0,0 +1,113 @@
+#!/usr/bin/env python3
+# /// script
+# requires-python = ">=3.9"
+# dependencies = ["pyshp", "shapely"]
+# ///
+"""Convert Natural Earth shapefile to Vanetza country data binary format.
+
+Downloads the Natural Earth admin-0 countries shapefile at the requested
+resolution, then converts it to a compact binary format.
+
+Output format:
+  version   : uint16 (little-endian)
+  followed by a sequence of entries, each:
+    m49_code  : uint16 (little-endian)
+    wkb_size  : uint32 (little-endian)
+    wkb_data  : bytes (OGC WKB MultiPolygon)
+"""
+import argparse
+import struct
+import sys
+import urllib.request
+import zipfile
+from pathlib import Path
+
+import shapefile
+from shapely.geometry import MultiPolygon, Polygon, shape
+
+RESOLUTIONS = ["110m", "50m", "10m"]
+FORMAT_VERSION = 1
+
+
+def download_shapefile(resolution: str, cache_dir: Path) -> Path:
+    name = f"ne_{resolution}_admin_0_countries"
+    shp_dir = cache_dir / name
+    shp_path = shp_dir / f"{name}.shp"
+
+    if shp_path.exists():
+        return shp_path
+
+    url = f"https://naciscdn.org/naturalearth/{resolution}/cultural/{name}.zip"
+    print(f"Downloading {url} ...", file=sys.stderr)
+    data, _ = urllib.request.urlretrieve(url)
+    with zipfile.ZipFile(data) as zf:
+        shp_dir.mkdir(parents=True, exist_ok=True)
+        zf.extractall(shp_dir)
+
+    return shp_path
+
+
+def convert(shp_path: Path, output: Path):
+    sf = shapefile.Reader(str(shp_path))
+    fields = [f[0] for f in sf.fields[1:]]  # skip DeletionFlag
+
+    if "ISO_N3_EH" not in fields:
+        print("Error: shapefile missing ISO_N3_EH field", file=sys.stderr)
+        sys.exit(1)
+
+    iso_n3_eh_idx = fields.index("ISO_N3_EH")
+    count = 0
+    skipped = 0
+
+    with open(output, "wb") as out:
+        out.write(struct.pack("<H", FORMAT_VERSION))
+
+        for sr in sf.shapeRecords():
+            iso_n3_eh = sr.record[iso_n3_eh_idx]
+
+            # Skip non-numeric codes (e.g., "-99" for disputed territories)
+            try:
+                m49 = int(iso_n3_eh)
+            except (ValueError, TypeError):
+                skipped += 1
+                continue
+
+            if m49 < 0 or m49 > 65535:
+                skipped += 1
+                continue
+
+            geom = shape(sr.shape.__geo_interface__)
+
+            # Normalize to MultiPolygon
+            if isinstance(geom, Polygon):
+                geom = MultiPolygon([geom])
+            elif not isinstance(geom, MultiPolygon):
+                skipped += 1
+                continue
+
+            wkb = geom.wkb
+
+            out.write(struct.pack("<H", m49))
+            out.write(struct.pack("<I", len(wkb)))
+            out.write(wkb)
+            count += 1
+
+    print(f"Wrote {count} countries, skipped {skipped} entries", file=sys.stderr)
+
+
+def main():
+    parser = argparse.ArgumentParser(description="Convert Natural Earth to country data binary")
+    parser.add_argument("--output", required=True, type=Path, help="Path to output .bin file")
+    parser.add_argument("--resolution", choices=RESOLUTIONS, default="50m",
+                        help="Natural Earth resolution (default: 50m)")
+    parser.add_argument("--cache-dir", type=Path,
+                        default=Path(__file__).parent / "cache",
+                        help="Cache directory for downloaded shapefiles")
+    args = parser.parse_args()
+
+    shp_path = download_shapefile(args.resolution, args.cache_dir)
+    convert(shp_path, args.output)
+
+
+if __name__ == "__main__":
+    main()