Revive yaris-obd: USB OBD adapter, real GPS/GNSS, offline map, hotspot, SQLite logging, dashcam retrieval

Squashed rewrite of the project revival work (replaces prior history on this
branch to remove personal data that had been accidentally committed - real
LAN IP, GPS coordinates, home WiFi SSID, and phone model). See PLAN.md for
full phase-by-phase details. Summary:

- Phase 2: adapt app_obd.py for a USB OBD-II adapter (was Bluetooth-only),
  auto-detect /dev/ttyUSB*, fix several pre-existing crash bugs.
- Phase 3/4: make the web UI work fully offline (vendored Socket.IO/Leaflet/
  Chart.js/FontAwesome, offline map tile downloader script, live GPS marker
  tracking fix).
- Phase 5: systemd deployment/autostart on the Pi.
- Phase 6: WiFi hotspot mode via NetworkManager (auto-switch between home
  WiFi and a local AP for in-car web UI access), mDNS hostname + port 80
  redirect so the UI is reachable at a plain hostname with no port number.
- Phase 7: fix app_db.py/app_sql.py bugs, wire up local SQLite trip logging.
- Phase 8: brand-agnostic USB dashcam file retrieval (lsblk transport-based
  detection, works with any dashcam brand/folder layout).
- Rewritten readme.md with a proper project overview.

Co-authored-by: Copilot <[email protected]>

deploy/install_service.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+# One-time install of the yaris-obd systemd service on the Pi.
+# Run this ON THE PI as the `yaris` user (needs sudo for the systemctl bits):
+#   cd /home/yaris/app/yaris-obd && bash deploy/install_service.sh
+set -euo pipefail
+
+REPO_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+SERVICE_FILE="$REPO_DIR/deploy/yaris-obd.service"
+SERVICE_NAME="yaris-obd.service"
+
+if [ ! -d "$REPO_DIR/venv" ]; then
+    echo "No venv found at $REPO_DIR/venv - creating one and installing requirements..."
+    python3 -m venv "$REPO_DIR/venv"
+    "$REPO_DIR/venv/bin/pip" install --upgrade pip
+    "$REPO_DIR/venv/bin/pip" install -r "$REPO_DIR/requirements.txt"
+fi
+
+sudo cp "$SERVICE_FILE" "/etc/systemd/system/$SERVICE_NAME"
+sudo systemctl daemon-reload
+sudo systemctl enable "$SERVICE_NAME"
+sudo systemctl restart "$SERVICE_NAME"
+
+echo "Done. Check status with: sudo systemctl status $SERVICE_NAME"
+echo "Logs: tail -f $REPO_DIR/yaris-obd.log  (or: sudo journalctl -u $SERVICE_NAME -f)"