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/ClockScreen.h

@@ -314,10 +314,8 @@ void UITask::buildClock() {
     lv_obj_set_flex_align(on, LV_FLEX_ALIGN_START, LV_FLEX_ALIGN_CENTER, LV_FLEX_ALIGN_CENTER);
     lv_obj_set_style_pad_column(on, 8, 0);
     lv_obj_set_style_pad_bottom(on, 4, 0);
-    lv_obj_t* sw = s_alarm_sw = lv_switch_create(on);
+    lv_obj_t* sw = s_alarm_sw = switchCreate(on, _prefs->alarm_on, nullptr, nullptr);
     label(on, "Alarm on", THEME_FONT_SMALL, theme::TEXT_MUTED);
-    lv_obj_set_size(sw, 50, 26);
-    if (_prefs->alarm_on) lv_obj_add_state(sw, LV_STATE_CHECKED);
     lv_obj_add_event_cb(sw, onAlarmSwitch, LV_EVENT_VALUE_CHANGED, NULL);
     label(col, "Repeat", THEME_FONT_SMALL, theme::TEXT_MUTED);
     char opts[48];