Contacts: cap chunked save to twice a day; flush on low battery

Throttle the ESP32 lazy contact save from a 5s debounce to a 12h
interval (CONTACTS_SAVE_INTERVAL). A new _nextContactSaveDue anchors
the next flush 12h out on the first dirty pass and only writes once
reached, clearing after each save so the next dirty event re-anchors.
Cuts the recurring ~95KB LittleFS rewrites on busy meshes. nRF52/STM32
blocking-save path unchanged.

Flush contacts (blocking) in the AUTO_SHUTDOWN_MILLIVOLTS path before
shutdown() so low-battery power-off doesn't drop up to 12h of contact
learning. Manual power-off left untouched.

Gate the SHUTDOWN home page out on the watch (MECK_TWATCH): removed
from the HomePage enum with render/input/isOnShutdownPage guarded.
The AXP2101 PWR-button long-press is the shutdown path there.

Files: MyMesh.h, MyMesh.cpp, UITask.cpp

examples/companion_radio/MyMesh.cpp

@@ -119,6 +119,7 @@
 #define DIRECT_SEND_PERHOP_EXTRA_MILLIS 250
 #define LAZY_CONTACTS_WRITE_DELAY       5000
 #define USER_IDLE_SAVE_THRESHOLD       15000  // Defer saves until 15s after last keypress
+#define CONTACTS_SAVE_INTERVAL       43200000  // 12h: cap chunked contact flush to twice a day
 
 #define PUBLIC_GROUP_PSK                "izOH6cXN6mrJ5e26oRXNcg=="
 
@@ -1495,6 +1496,7 @@ MyMesh::MyMesh(mesh::Radio &radio, mesh::RNG &rng, mesh::RTCClock &rtc, SimpleMe
   next_ack_idx = 0;
   sign_data = NULL;
   dirty_contacts_expiry = 0;
+  _nextContactSaveDue = 0;
   advert_paths = nullptr;  // PSRAM-allocated in begin()
   _rxlog = nullptr;        // PSRAM-allocated in begin()
   _rxlog_head = 0;
@@ -3714,8 +3716,15 @@ void MyMesh::loop() {
       // Voice session or active keyboard use -- push save forward
       dirty_contacts_expiry = futureMillis(2000);
     } else if (!_store->isSaveInProgress()) {
-      _store->beginSaveContacts(this);
-      dirty_contacts_expiry = 0;
+      // Cap the chunked flush to CONTACTS_SAVE_INTERVAL (twice a day): anchor
+      // the next-due time on the first dirty pass, then only write once it is
+      // reached. Cleared after a save so the next dirty event re-anchors.
+      if (_nextContactSaveDue == 0) _nextContactSaveDue = futureMillis(CONTACTS_SAVE_INTERVAL);
+      if (millisHasNowPassed(_nextContactSaveDue)) {
+        _store->beginSaveContacts(this);
+        dirty_contacts_expiry = 0;
+        _nextContactSaveDue = 0;
+      }
     }
 #endif
   }

examples/companion_radio/MyMesh.h

@@ -346,6 +346,7 @@ private:
   uint8_t *sign_data;
   uint32_t sign_data_len;
   unsigned long dirty_contacts_expiry;
+  unsigned long _nextContactSaveDue;   // ESP32 chunked save: next scheduled flush (0 = unscheduled)
 
   TransportKey send_scope;
 

examples/companion_radio/ui-new/UITask.cpp

@@ -183,7 +183,9 @@ class HomeScreen : public UIScreen {
 #if HAS_BQ27220
     BATTERY,
 #endif
+#if !defined(MECK_TWATCH)
     SHUTDOWN,
+#endif
     Count    // keep as last
   };
 
@@ -366,7 +368,11 @@ public:
   bool isEditingUTC() const { return _editing_utc; }
   bool isFirstPage() const { return _page == HomePage::FIRST; }
   bool isOnRecentPage() const { return _page == HomePage::RECENT; }
+#if defined(MECK_TWATCH)
+  bool isOnShutdownPage() const { return false; }
+#else
   bool isOnShutdownPage() const { return _page == HomePage::SHUTDOWN; }
+#endif
   void cancelEditing() { 
     if (_editing_utc) {
       _node_prefs->utc_offset_hours = _saved_utc_offset;
@@ -1260,7 +1266,9 @@ public:
       sprintf(buf, "%d.%d C", battTemp / 10, abs(battTemp % 10));
       display.drawTextRightAlign(display.width()-1-EINK_X_OFFSET, y, buf);
 #endif
-    } else if (_page == HomePage::SHUTDOWN) {
+    }
+#if !defined(MECK_TWATCH)
+    else if (_page == HomePage::SHUTDOWN) {
       display.setColor(DisplayDriver::GREEN);
       display.setTextSize(1);
       if (_shutdown_init) {
@@ -1304,6 +1312,7 @@ public:
         display.drawTextCentered(display.width() / 2, y2, line2);
       }
     }
+#endif
     return _editing_utc ? 700 : 5000;
   }
 
@@ -1342,6 +1351,7 @@ public:
       return true;  // Consume all other keys while editing
     }
 
+#if !defined(MECK_TWATCH)
     // SHUTDOWN page -- intercept up/down and Enter before page cycling
     if (_page == HomePage::SHUTDOWN) {
       if (_poweroff_confirm) {
@@ -1376,6 +1386,7 @@ public:
       }
       // Left/right fall through to page cycling below
     }
+#endif
 
     if (c == KEY_LEFT || c == KEY_PREV || c == 'a') {
       _page = (_page + HomePage::Count - 1) % HomePage::Count;
@@ -2894,6 +2905,10 @@ if (curr) curr->poll();
       }
       #endif
 
+      // Flush contacts before the battery dies -- the chunked lazy save may not
+      // have run for hours. Blocking save (tmp-then-rename, brownout-safe).
+      the_mesh.saveContacts();
+
       shutdown();
       }
     } else {