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/fuzz-harness/Dockerfile

@@ -0,0 +1,15 @@
+ARG VERSION=latest
+FROM aflplusplus/aflplusplus:${VERSION}
+
+# install build dependencies for Vanetza
+RUN apt-get update && apt-get install --no-install-recommends -y \
+    libboost-all-dev libcrypto++-dev libgeographic-dev libssl-dev
+
+# install casr-afl tool
+RUN cargo install --root /usr/local casr
+
+# set up "fuzz" user and mapping of host user
+RUN useradd -m -s /bin/bash fuzz
+RUN cp /root/.bashrc /home/fuzz/.bashrc && chown fuzz:fuzz /home/fuzz/.bashrc
+COPY docker-entrypoint.sh /docker-entrypoint.sh
+ENTRYPOINT ["/docker-entrypoint.sh"]