feat(ui-lvgl): title bar with the clock, tidier controls, contextual nav bar

Density from less chrome instead of smaller rows (ROW_H stays 44):
- titled screens drop the status bar; the title bar (APPBAR_H) holds back,
  the title, the screen's actions and the time/battery on a pill; the status
  bar returns for Home, the map, typing, the quick panel and the lock
- one radius (RADIUS) for everything tapped: buttons, tabs, choices, chips
- tabs are all segmented at TAB_H in the body (GPS, Clock converted)
- Nodes: chips row + sort + status line become one toolbar row with
  Show / Order choices; Messages' All/Favourites is the same choice
- nav map: the target bar only while there is a target; the pin opens one
  "Places" popup; back from a map options page restores the map and Map
  tools as left, without a jump
- node detail actions at the top of the scroll; Home tiles fill the page
- rowsFit() leaves growing labels to the flex (a screen title cut to one
  letter after Messages' filter changed)

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

examples/companion_radio/ui-lvgl/DiagScreen.h

@@ -336,7 +336,7 @@ void UITask::buildDiag() {
   if (s_tab == TAB_LIVE && _header) headerButton(_header, LV_SYMBOL_REFRESH " Reset", onDiagReset, 4, NULL);
 
   static const char* TABS[] = { "Live", "History", "System", "Font", "Noise", "" };
-  lv_obj_t* tabs = segmented(body, TABS, s_tab, lv_pct(100), 34);
+  lv_obj_t* tabs = segmented(body, TABS, s_tab, lv_pct(100), theme::TAB_H);
   lv_obj_set_style_bg_color(tabs, lv_color_hex(theme::SURFACE), LV_PART_ITEMS);
   lv_obj_add_event_cb(tabs, onDiagTab, LV_EVENT_VALUE_CHANGED, NULL);