feat: add 12h/24h clock format setting (default 24h)

Toggle in Settings > Display > Format. In 12h mode the clock shows
h:mm AM/PM (or h:mm:ss AM/PM with seconds, no space before AM/PM).

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

examples/companion_radio/DataStore.cpp

@@ -285,6 +285,9 @@ void DataStore::loadPrefsInt(const char *filename, NodePrefs& _prefs, double& no
                                 file.read((uint8_t *)_prefs.dm_melody, sizeof(_prefs.dm_melody));
                                 if (file.available()) {
                                   file.read((uint8_t *)&_prefs.auto_lock, sizeof(_prefs.auto_lock));
+                                  if (file.available()) {
+                                    file.read((uint8_t *)&_prefs.clock_12h, sizeof(_prefs.clock_12h));
+                                  }
                                 }
                               }
                             }
@@ -375,6 +378,7 @@ void DataStore::savePrefs(const NodePrefs& _prefs, double node_lat, double node_
     file.write((uint8_t *)&_prefs.ch_notif_melody_2, sizeof(_prefs.ch_notif_melody_2));
     file.write((uint8_t *)_prefs.dm_melody, sizeof(_prefs.dm_melody));
     file.write((uint8_t *)&_prefs.auto_lock, sizeof(_prefs.auto_lock));
+    file.write((uint8_t *)&_prefs.clock_12h, sizeof(_prefs.clock_12h));
 
     file.close();
   }

examples/companion_radio/NodePrefs.h

@@ -57,6 +57,7 @@ struct NodePrefs {  // persisted to file
   char     bot_reply_dm[140];   // auto-reply text for DM
   char     bot_reply_ch[140];   // auto-reply text for channel
   uint8_t  clock_hide_seconds; // 0=show HH:MM:SS/refresh 1s (default), 1=hide/refresh 60s
+  uint8_t  clock_12h;          // 0=24h (default), 1=12h with AM/PM
   uint8_t  buzzer_auto;        // 0=manual (default), 1=auto-mute when BT connected
   struct DmNotifEntry { uint8_t prefix[4]; uint8_t state; }; // state: 0=default,1=muted,2=force-on
   static const int DM_NOTIF_TABLE_MAX = 16;

examples/companion_radio/ui-new/SettingsScreen.h

@@ -13,6 +13,7 @@ class SettingsScreen : public UIScreen {
     AUTO_LOCK,
     BATT_DISPLAY,
     CLOCK_SECONDS,
+    CLOCK_FORMAT,
     // Sound section
     SECTION_SOUND,
     BUZZER,
@@ -311,6 +312,10 @@ class SettingsScreen : public UIScreen {
       display.print("Seconds");
       display.setCursor(VAL_X, y);
       display.print((p && p->clock_hide_seconds) ? "OFF" : "ON");
+    } else if (item == CLOCK_FORMAT) {
+      display.print("Format");
+      display.setCursor(VAL_X, y);
+      display.print((p && p->clock_12h) ? "12h" : "24h");
     } else if (item == DM_FILTER) {
       display.print("DM");
       display.setCursor(VAL_X, y);
@@ -496,6 +501,11 @@ public:
       _dirty = true;
       return true;
     }
+    if (_selected == CLOCK_FORMAT && p && (left || right || enter)) {
+      p->clock_12h ^= 1;
+      _dirty = true;
+      return true;
+    }
     if (_selected == DM_FILTER && p && (left || right || enter)) {
       p->dm_show_all = p->dm_show_all ? 0 : 1;
       _dirty = true;

examples/companion_radio/ui-new/UITask.cpp

@@ -389,10 +389,16 @@ public:
         display.setColor(DisplayDriver::LIGHT);
         display.setTextSize(2);
         bool show_sec = !_node_prefs || !_node_prefs->clock_hide_seconds;
-        if (show_sec)
+        bool h12 = _node_prefs && _node_prefs->clock_12h;
-          sprintf(buf, "%02d:%02d:%02d", ti->tm_hour, ti->tm_min, ti->tm_sec);
+        if (h12) {
-        else
+          int h = ti->tm_hour % 12; if (h == 0) h = 12;
-          sprintf(buf, "%02d:%02d", ti->tm_hour, ti->tm_min);
+          const char* ap = ti->tm_hour < 12 ? "AM" : "PM";
+          if (show_sec) sprintf(buf, "%d:%02d:%02d%s", h, ti->tm_min, ti->tm_sec, ap);
+          else          sprintf(buf, "%d:%02d %s", h, ti->tm_min, ap);
+        } else {
+          if (show_sec) sprintf(buf, "%02d:%02d:%02d", ti->tm_hour, ti->tm_min, ti->tm_sec);
+          else          sprintf(buf, "%02d:%02d", ti->tm_hour, ti->tm_min);
+        }
         display.drawTextCentered(display.width() / 2, 0, buf);
 
         display.setTextSize(1);
@@ -1334,7 +1340,12 @@ void UITask::loop() {
         struct tm* ti = gmtime(&t);
         char buf[12];
         _display->setTextSize(2);
-        sprintf(buf, "%02d:%02d", ti->tm_hour, ti->tm_min);
+        if (_node_prefs && _node_prefs->clock_12h) {
+          int h = ti->tm_hour % 12; if (h == 0) h = 12;
+          sprintf(buf, "%d:%02d %s", h, ti->tm_min, ti->tm_hour < 12 ? "AM" : "PM");
+        } else {
+          sprintf(buf, "%02d:%02d", ti->tm_hour, ti->tm_min);
+        }
         _display->drawTextCentered(_display->width() / 2, 8, buf);
         _display->setTextSize(1);
         static const char* wd[] = {"Sun","Mon","Tue","Wed","Thu","Fri","Sat"};