Keep the colleague's microbu-esp32c5 tree in this repository

obu-firmware builds against vanetza-idf from microbu-esp32c5/external, but
that tree was gitignored, so a clone of this repository could not build the
firmware it ships. It is now committed here as ordinary files in its own
folder, microbu-esp32c5/: the colleague's commit cf4b99f plus the V2X2MAP
bridge's signature verification (--trust) used on the bench. Nothing is
fetched from or pushed to the colleague's repository; this repository and
its remotes carry everything. The folder's own .gitignore keeps build output,
downloaded components and private key material out, as it did there; the
committed file set is identical to that repository's tracked files.

The ESP32-C5 is still flashed from obu-firmware/, which only takes
vanetza-idf from microbu-esp32c5/, so the two stay separate folders.
FLASHING.md says how to take a newer version of the colleague's tree (copy
it over the folder, rebuild, test, commit).

microbu-esp32c5/tools/v2x2map-0.3.0/README.md

@@ -0,0 +1,35 @@
+# V2X2MAP bridge (vendored, bridge-only)
+
+This is a pruned copy of the `bridge/` component of
+[V2X2MAP](https://github.com/711it/v2x2map) 0.3.0, a receiver/live-map tool
+for ITS-G5 V2X traffic. V2X2MAP is itself a fork of
+[opentrafficmap/its-g5-receiver-firmware](https://codeberg.org/opentrafficmap/its-g5-receiver-firmware)
+extended with BLE streaming, an Android app and a Windows installer — see
+[the upstream project](https://github.com/711it/v2x2map) for the full
+firmware/Android/iOS sources and license (MIT, `LICENSE` in this directory).
+
+## Why it is here
+
+`bridge/` is the host-side Python tool (serial/BLE ingestion, dashboard,
+recording, VAM/CAM decoding) used for prototyping and to sanity-check VAM
+decoding independently of this project's own `external/vanetza-idf`
+stack. It has been locally modified to decode VAMs (`bridge/vam.py`,
+`bridge/test_vam.py`, `bridge/asn1/`) and, since 2026-09-14, to look inside
+signed GeoNetworking packets (`bridge/secured.py`: a bounded COER walk of the
+TS 103 097 `Ieee1609Dot2Data` that returns the unsecured payload, PSID,
+generation time and signer; the signature is **not** verified, the dashboard
+says "signed … not verified").
+
+The Android app and the receiver firmware from the original project are not
+carried into this repository; this project uses its own ESP32-C5 firmware
+(`firmware/`, `external/vanetza-idf/`) instead.
+`bridge/firmware/*.bin` is a small set of prebuilt images kept only so the
+bridge's recording/decode workflow can be exercised against a receiver board
+without a separate firmware build.
+
+## Use
+
+See `bridge/its_g5_bridge.py` and `bridge/dashboard_server.py` for the
+serial/BLE bridge and local dashboard; `bridge/vam.py` for the VAM decode
+path. `bridge/requirements.txt` lists its Python dependencies (separate from
+this project's own `station-link/python/requirements.txt`).