After rebasing onto upstream/dev, app.py contained an inline
_get_version_info() duplicating logic already centralized in
modules/version_info.py. Replace with a 5-line delegate to
resolve_runtime_version(), removing the now-unnecessary import subprocess.
Also refreshes tests/fixtures/mqtt_packets.json with current live MQTT
fixture timestamps.
Behavioral note: in a bare dev clone with no .version_info and no
MESHCORE_BOT_VERSION env var, the footer now shows the pyproject.toml
version (v0.1.0) instead of branch·commit·date. Production deployments
are unaffected.
Do not merge until #149 is merged.
