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/gpsnc.sh

@@ -0,0 +1,25 @@
+#!/bin/sh
+GPSD_LOCAL_PORT=8051
+NMEA_REMOTE_PORT=8052
+NC_REMOTE_PID=0
+NC_LOCAL_PID=0
+FIFO=/tmp/gpsnc_fifo.$$
+
+exit_handler()
+{
+    kill $NC_REMOTE_PID 2>/dev/null
+    kill $NC_LOCAL_PID 2>/dev/null
+    rm -f $FIFO
+}
+
+trap exit_handler SIGINT SIGTERM
+
+mkfifo $FIFO
+nc -k -l ${NMEA_REMOTE_PORT} > $FIFO &
+NC_REMOTE_PID=$!
+nc -l ${GPSD_LOCAL_PORT} < $FIFO &
+NC_LOCAL_PID=$!
+
+sleep 1 # wait for nc ports becoming available
+gpsd -n -N -D4 tcp://localhost:${GPSD_LOCAL_PORT}
+