Ignore the vanetza checkout and Python bytecode caches

vanetza is a clone of the open-source ETSI C-ITS stack, kept beside the
project as a reference in the same way as C-ITS-Parser. It is read, not
built, and it carries its own .git, so a plain `git add .` would have
picked it up as an embedded repository.

__pycache__/ appears when obu-firmware/test/host/check_replay.py is
imported rather than run.

.gitignore

@@ -27,6 +27,9 @@ secrets.properties
 /.idea/appInsightsSettings.xml
 /.idea/studiobot.xml
 
+# Python bytecode caches, e.g. from importing obu-firmware/test/host/check_replay.py.
+__pycache__/
+
 # ESP-IDF rewrites sdkconfig on every build and keeps the previous one here.
 # sdkconfig.defaults is the real, intentional configuration; these two are output.
 sdkconfig.old
@@ -38,6 +41,7 @@ sdkconfig.old
 # Third-party working copies kept beside the project, not part of it. The ASN.1
 # modules this project actually needs are vendored under asn1/ instead.
 /C-ITS-Parser/
+/vanetza/
 
 # Office lock files. Word/Excel create these beside a document while it is open
 # and remove them on close, so they are transient and machine-local.