Phase 23: UI redesign — responsive mobile + desktop layout

- Replace SB Admin 2 sidebar with a clean fixed sidebar (desktop)
  and a sticky bottom tab navigation (mobile, ≤767px)
- Sidebar collapses to icon-only mode with state persisted in localStorage
- Logo is a functional home link on all viewports
- Mobile: full-width content, bottom nav replaces sidebar
- Dashboard: 6 OBD stat cards (status, speed, RPM, coolant, throttle, fuel)
  wired to live socket events; removed all placeholder buttons/dropdowns
- GPS info section cleaned up (lat/lon display instead of X/Y paragraphs)
- DTC page: live /api/dtc wiring — MIL indicator + DTC table populated from API
- New /api/dtc route added to app.py (mil + codes)
- yaris.js: added obd_coolant_temp / obd_fuel_level / obd_throttle listeners
- yaris.css: full rewrite — layout variables, sidebar, bottom nav, OBD cards,
  border-start utilities, mobile padding for bottom nav

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

app.py

@@ -210,6 +210,13 @@ def data():
     response.content_type = 'application/json'
     return response
 
+@app.route('/api/dtc')
+def api_dtc():
+    return jsonify({
+        "mil": app_obd.get_fresh_mil(),
+        "codes": app_obd.get_fresh_dtc_codes(),
+    })
+
 if __name__ == '__main__':
     # Debug/Development
     # app.run(debug=True, host="0.0.0.0", port="5000")