refactor: one copy of shared logic and widgets; GPS is asked for, not switched on silently

Duplicates found between the L1 and L2 frontends, and inside the L2 one:
- geo::fmtLocShare / fmtLatLon / turnDeg / isAhead (GeoUtils.h): the [LOC]
  text was built in five places, the turn angle and its "ahead" threshold in
  both navigations, coordinates by hand in nine. Tested.
- LiveShareEngine::setEnabled: live share was switched in three places.
- L1 waypoint share uses WaypointModel::shareText; Trail's "Share my pos"
  goes through UITask::quickShareMyLocation, so it now sends to a running
  live-share session as the home Map page does.
- L2 Widgets.h: switchCreate (one switch size, was four), switchRow with a
  state and callback (16 hand-wired copies), switchRowOpens (Bluetooth, WiFi,
  GPS), primaryButton (one height for Save / Measure / New area / Update).

GPS: with it off, starting the trail, live share or track back, sharing or
marking a position, or centring the map asks first ("GPS is off") on both
L1 and L2; Cancel leaves it undone. A share or a mark waits for a fresh fix
(a switched-off module may still report its last one), which also fixes the
L1 "Share my pos" sending a stale position. SOS still turns the GPS on itself.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

examples/companion_radio/ui-lvgl/QuickScreen.h

@@ -202,15 +202,11 @@ void UITask::advertSend(bool flood) {
 static void bluetoothRow(lv_obj_t* body) {
   char sub[48];
   qview::bluetoothHint(sub, sizeof(sub));
-  lv_obj_t* sw = switchRow(body, LV_SYMBOL_BLUETOOTH "  Bluetooth", sub, nullptr);
-  if (s_ui->isBluetoothEnabled()) lv_obj_add_state(sw, LV_STATE_CHECKED);
-  lv_obj_add_event_cb(sw, qview::onBtSwitch, LV_EVENT_VALUE_CHANGED, NULL);
+  lv_obj_t* sw = switchRow(body, LV_SYMBOL_BLUETOOTH "  Bluetooth", sub, s_ui->isBluetoothEnabled(), qview::onBtSwitch);
 #ifdef BLE_PIN_CODE
-  lv_obj_t* row = lv_obj_get_parent(sw);
-  rowPressable(row);
-  lv_obj_add_event_cb(row, [](lv_event_t* e) {
-    if (lv_event_get_target(e) == lv_event_get_current_target(e)) onBlePin(e);   // not the switch
-  }, LV_EVENT_CLICKED, NULL);
+  switchRowOpens(sw, onBlePin);
+#else
+  (void)sw;
 #endif
 }