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/security/SingleEtsiTs103097Certificate.h

@@ -0,0 +1,38 @@
+/*
+ * Generated by asn1c
+ * From ASN.1 module "EtsiTs103097Module"
+ * 	found in "TS103097v131.asn"
+ * 	`asn1c -fcompound-names -fincludes-quoted -no-gen-example -fprefix=Vanetza_Security_ -R`
+ */
+
+#ifndef	_Vanetza_Security_SingleEtsiTs103097Certificate_H_
+#define	_Vanetza_Security_SingleEtsiTs103097Certificate_H_
+
+
+#include "asn_application.h"
+
+/* Including external dependencies */
+#include "EtsiTs103097Certificate.h"
+#include "constr_SEQUENCE.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Vanetza_Security_SingleEtsiTs103097Certificate */
+typedef struct Vanetza_Security_SingleEtsiTs103097Certificate {
+	Vanetza_Security_EtsiTs103097Certificate_t	 only;
+	
+	/* Context for parsing across buffer boundaries */
+	asn_struct_ctx_t _asn_ctx;
+} Vanetza_Security_SingleEtsiTs103097Certificate_t;
+
+/* Implementation */
+extern asn_TYPE_descriptor_t asn_DEF_Vanetza_Security_SingleEtsiTs103097Certificate;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif	/* _Vanetza_Security_SingleEtsiTs103097Certificate_H_ */
+#include "asn_internal.h"