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/dcc/limeric_transmit_rate_control.cpp

@@ -0,0 +1,35 @@
+#include "limeric_transmit_rate_control.hpp"
+#include <vanetza/common/runtime.hpp>
+
+namespace vanetza
+{
+namespace dcc
+{
+
+LimericTransmitRateControl::LimericTransmitRateControl(const Runtime& rt, const Limeric& limeric) :
+    m_budget(limeric, rt)
+{
+}
+
+Clock::duration LimericTransmitRateControl::delay(const Transmission&)
+{
+    return m_budget.delay();
+}
+
+Clock::duration LimericTransmitRateControl::interval(const Transmission&)
+{
+    return m_budget.interval();
+}
+
+void LimericTransmitRateControl::notify(const Transmission& transmission)
+{
+    m_budget.notify(transmission.channel_occupancy());
+}
+
+void LimericTransmitRateControl::update()
+{
+    m_budget.update();
+}
+
+} // namespace dcc
+} // namespace vanetza