fix: persist car-connected flag so trip building works across reboots (BUG-16)

connect_obd() set _car_ever_connected without a global declaration, so the
module-level flag was never set and was_car_ever_connected() always returned
False — local trip building has been silently blocked since BUG-10 landed.
Also persist the flag to the settings table so a drive followed by a reboot
still builds trips, and clean up dead code in was_car_ever_connected().

modules/app_obd.py

@@ -165,6 +165,7 @@ def _log_connection_diagnostics(candidate):
 def connect_obd():
     """Connect to the adapter and ECU, with actionable failure diagnostics."""
     global connection
+    global _car_ever_connected
     with _connect_lock:
         if _is_car_connected():
             return connection
@@ -232,6 +233,7 @@ def connect_obd():
             connection = candidate
         if candidate is not None:
             _car_ever_connected = True
+            _persist_car_connected()
 
         if candidate is None:
             _emit_disconnected()
@@ -274,15 +276,28 @@ def obd_connection():
     start_obd()
 
 
+def _persist_car_connected():
+    """Record that the car ECU has been reached, so trip building keeps working
+    across reboots (the in-memory flag resets every process start)."""
+    try:
+        from modules import app_sql
+        app_sql.set_setting("car_ever_connected", "1")
+    except Exception as error:
+        print("Failed to persist car-connected flag:", error)
+
+
 def was_car_ever_connected():
-    """True if the car ECU has been reached at least once this session."""
+    """True if the car ECU has ever been reached (persisted across restarts)."""
+    global _car_ever_connected
+    if _car_ever_connected:
+        return True
+    try:
+        from modules import app_sql
+        if app_sql.get_setting("car_ever_connected", "0") == "1":
+            _car_ever_connected = True
+    except Exception:
+        pass
     return _car_ever_connected
-    if _is_car_connected():
-        app_events.socketio.emit("obd_status", obd_status[1])
-        app_events.socketio.emit("obd_speed", get_speedtime())
-        app_events.socketio.emit("obd_rpm", rpm if rpm is not None else "-")
-    else:
-        _emit_disconnected()
 
 
 def get_fresh_mil(max_age=SENSOR_POLL_INTERVAL * 3):