feat(eink): suppress clock seconds to prevent per-second panel refreshes

E-ink panels take ~2 s for a full refresh and visible flicker on every update.
Showing seconds caused the clock page to redraw every 1 s, triggering a real
panel refresh each time the CRC changed.

- Default clock_hide_seconds=1 for EINK_DISPLAY_MODEL builds so fresh
  installs don't flicker out of the box.
- Remove the Seconds setting from SettingsScreen on e-ink so users can't
  accidentally re-enable it.
- Clock page now returns 60 s refresh interval on e-ink (content changes at
  most once per minute); other home pages capped at 30 s (new messages still
  force immediate redraw via notify()).
- Lock screen refresh interval raised from 1 s to 60 s on e-ink; button
  presses already reset _next_refresh=0, so unlock feedback is instant.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

examples/companion_radio/MyMesh.cpp

@@ -952,6 +952,9 @@ MyMesh::MyMesh(mesh::Radio &radio, mesh::RNG &rng, mesh::RTCClock &rtc, SimpleMe
   _prefs.dm_show_all = 1;        // show all contacts by default
   memset(_prefs.dm_notif, 0, sizeof(_prefs.dm_notif));
   _prefs.auto_off_secs = 15;    // 15 seconds auto-off by default
+#ifdef EINK_DISPLAY_MODEL
+  _prefs.clock_hide_seconds = 1;  // e-ink: seconds cause a panel refresh every second
+#endif
   _prefs.tz_offset_hours = 0;  // UTC by default
   _prefs.low_batt_mv = 3400;  // auto-shutdown at 3.4V by default
   _prefs.batt_display_mode = 0; // icon by default

examples/companion_radio/ui-new/SettingsScreen.h

@@ -12,7 +12,9 @@ class SettingsScreen : public UIScreen {
     AUTO_OFF,
     AUTO_LOCK,
     BATT_DISPLAY,
+#if !defined(EINK_DISPLAY_MODEL)
     CLOCK_SECONDS,
+#endif
     CLOCK_FORMAT,
     FONT,
 #if defined(EINK_DISPLAY_MODEL)
@@ -312,10 +314,12 @@ class SettingsScreen : public UIScreen {
       display.setCursor(VAL_X, y);
       uint8_t mode = p ? p->batt_display_mode : 0;
       display.print(BATT_DISPLAY_LABELS[mode < BATT_DISPLAY_COUNT ? mode : 0]);
+#if !defined(EINK_DISPLAY_MODEL)
     } else if (item == CLOCK_SECONDS) {
       display.print("Seconds");
       display.setCursor(VAL_X, y);
       display.print((p && p->clock_hide_seconds) ? "OFF" : "ON");
+#endif
     } else if (item == CLOCK_FORMAT) {
       display.print("Format");
       display.setCursor(VAL_X, y);
@@ -512,11 +516,13 @@ public:
       if (left)  idx = (idx + BATT_DISPLAY_COUNT - 1) % BATT_DISPLAY_COUNT;
       if (left || right) { p->batt_display_mode = idx; _dirty = true; return true; }
     }
+#if !defined(EINK_DISPLAY_MODEL)
     if (_selected == CLOCK_SECONDS && p && (left || right || enter)) {
       p->clock_hide_seconds ^= 1;
       _dirty = true;
       return true;
     }
+#endif
     if (_selected == CLOCK_FORMAT && p && (left || right || enter)) {
       p->clock_12h ^= 1;
       _dirty = true;

examples/companion_radio/ui-new/UITask.cpp

@@ -692,11 +692,16 @@ public:
       }
     }
     bool auto_adv = _node_prefs && _node_prefs->advert_auto_interval_sec > 0;
+#ifdef EINK_DISPLAY_MODEL
+    if (_page == HomePage::CLOCK) return 60000;  // no seconds on e-ink; content changes at most every minute
+    return 30000;  // e-ink: limit base polling; new messages still force immediate refresh via notify()
+#else
     if (_page == HomePage::CLOCK) {
       bool show_sec = !_node_prefs || !_node_prefs->clock_hide_seconds;
       return auto_adv ? 1000 : (show_sec ? 1000 : 60000);
     }
     return auto_adv ? 1000 : 5000;
+#endif
   }
 
   bool handleInput(char c) override {
@@ -1399,7 +1404,11 @@ void UITask::loop() {
       _display->setCursor(hx, hy);
       _display->print(hint);
       _display->endFrame();
+#ifdef EINK_DISPLAY_MODEL
+      _next_refresh = millis() + 60000;
+#else
       _next_refresh = millis() + 1000;
+#endif
     } else if (!_locked && millis() >= _next_refresh && curr) {
       _display->startFrame();
       int delay_millis = curr->render(*_display);