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/vanetza/geodesy/position.hpp

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <vanetza/units/angle.hpp>
+#include <vanetza/units/length.hpp>
+
+namespace vanetza
+{
+namespace geodesy
+{
+
+/**
+ * Cartesian position.
+ * Point in an ENU (East-North-Up) coordinate system, units in meters.
+ */
+struct CartesianPosition
+{
+    CartesianPosition() : x(0.0 * units::si::meter), y(0.0 * units::si::meter) {}
+    CartesianPosition(units::Length x_, units::Length y_) : x(x_), y(y_) {}
+    units::Length x;
+    units::Length y;
+};
+
+CartesianPosition operator-(const CartesianPosition&, const CartesianPosition&);
+
+struct GeodeticPosition
+{
+    GeodeticPosition() :
+        latitude(0.0 * units::degree), longitude(0.0 * units::degree) {}
+    GeodeticPosition(units::GeoAngle lat, units::GeoAngle lon) :
+        latitude(lat), longitude(lon) {}
+    units::GeoAngle latitude;
+    units::GeoAngle longitude;
+};
+
+} // namespace geodesy
+} // namespace vanetza