fix: no flash writes while typing, and a clock that survives a power loss

Contacts and paths are saved a while after the change and never while the
user is active, so a send no longer stutters on the 53 KB contact rewrite
(a path that came back unchanged isn't written at all). The clock is saved
every 30 minutes and restored no earlier than the firmware's build day.

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

examples/companion_radio/ui-lvgl/UITask.cpp

@@ -1561,6 +1561,7 @@ void UITask::loop() {
       if (lvport::touched()) { lvport::swallowTouch(); wake(); }
     }
   } else {
+    if (lv_display_get_inactive_time(NULL) < 1000) the_mesh.noteUserInput();
     // Locked, nobody's using it: the lock screen goes dark after LOCK_OFF_MS
     // even with auto-off at Never (a woken-up pocket, a boot PIN, a message).
     uint32_t aoff = autoOffMillis();