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FLASHING.md says how to take a newer version of the colleague's tree (copy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/external/vanetza-idf/tools/socktap/time_trigger.hpp

@@ -0,0 +1,27 @@
+#ifndef TIME_TRIGGER_HPP_XRPGDYXO
+#define TIME_TRIGGER_HPP_XRPGDYXO
+
+#include <vanetza/common/manual_runtime.hpp>
+#include <boost/asio/io_context.hpp>
+#include <boost/asio/steady_timer.hpp>
+#include <boost/date_time/posix_time/posix_time_types.hpp>
+
+class TimeTrigger
+{
+public:
+    TimeTrigger(boost::asio::io_context&);
+    vanetza::Runtime& runtime() { return runtime_; }
+    void schedule();
+
+private:
+    boost::posix_time::ptime now() const;
+    void on_timeout(const boost::system::error_code&);
+    void update_runtime();
+
+    boost::asio::io_context& io_context_;
+    boost::asio::steady_timer timer_;
+    vanetza::ManualRuntime runtime_;
+};
+
+#endif /* TIME_TRIGGER_HPP_XRPGDYXO */
+