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/asn1/apply_patches.cmake

@@ -0,0 +1,10 @@
+find_package(Git REQUIRED)
+file(GLOB PATCH_FILES ${PATCH_DIRECTORY}/*.patch)
+foreach(PATCH_FILE IN LISTS PATCH_FILES)
+    get_filename_component(PATCH_NAME "${PATCH_FILE}" NAME_WE)
+    message(STATUS "Applying patch ${PATCH_NAME}")
+    execute_process(COMMAND "${GIT_EXECUTABLE}" apply "${PATCH_FILE}" RESULT_VARIABLE PATCH_RESULT)
+    if(NOT PATCH_RESULT EQUAL 0)
+        message(SEND_ERROR "Applying patch ${PATCH_FILE} failed!")
+    endif()
+endforeach()