Settings: add buzzer volume control (5 levels, like brightness)

- NodePrefs: add buzzer_volume field (0=min..4=max, default 4)
- DataStore: persist buzzer_volume at end of prefs file (backward-compat)
- buzzer: setVolume()/getVolume(); applyVolume() sets PWM duty cycle via
  analogWrite() after each rtttl::play() call to control output amplitude
- Settings UI: new BzrVol bar item in Sound section (left/right to adjust)
- UITask: apply saved volume on startup alongside brightness

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

examples/companion_radio/DataStore.cpp

@@ -244,6 +244,9 @@ void DataStore::loadPrefsInt(const char *filename, NodePrefs& _prefs, double& no
       file.read((uint8_t *)&_prefs.ch_notif_muted, sizeof(_prefs.ch_notif_muted));     // 1552
       file.read((uint8_t *)&_prefs.dm_show_all, sizeof(_prefs.dm_show_all));           // 1560
       file.read((uint8_t *)&_prefs.room_fav_only, sizeof(_prefs.room_fav_only));       // 1561
+      if (file.available()) {
+        file.read((uint8_t *)&_prefs.buzzer_volume, sizeof(_prefs.buzzer_volume));     // 1562
+      }
     }
 
     file.close();
@@ -295,6 +298,7 @@ void DataStore::savePrefs(const NodePrefs& _prefs, double node_lat, double node_
     file.write((uint8_t *)&_prefs.ch_notif_muted, sizeof(_prefs.ch_notif_muted));       // 1552
     file.write((uint8_t *)&_prefs.dm_show_all, sizeof(_prefs.dm_show_all));             // 1560
     file.write((uint8_t *)&_prefs.room_fav_only, sizeof(_prefs.room_fav_only));         // 1561
+    file.write((uint8_t *)&_prefs.buzzer_volume, sizeof(_prefs.buzzer_volume));         // 1562
 
     file.close();
   }

examples/companion_radio/MyMesh.cpp

@@ -864,6 +864,7 @@ MyMesh::MyMesh(mesh::Radio &radio, mesh::RNG &rng, mesh::RTCClock &rtc, SimpleMe
   _prefs.gps_enabled = 0;       // GPS disabled by default
   _prefs.gps_interval = 0;      // No automatic GPS updates by default
   _prefs.display_brightness = 2; // medium brightness by default
+  _prefs.buzzer_volume = 4;      // max volume by default
   _prefs.auto_off_secs = 15;    // 15 seconds auto-off by default
   _prefs.tz_offset_hours = 0;  // UTC by default
   _prefs.low_batt_mv = 3400;  // auto-shutdown at 3.4V by default

examples/companion_radio/NodePrefs.h

@@ -25,6 +25,7 @@ struct NodePrefs {  // persisted to file
   uint32_t ble_pin;
   uint8_t  advert_loc_policy;
   uint8_t  buzzer_quiet;
+  uint8_t  buzzer_volume;   // 0=min..4=max, default 4
   uint8_t  gps_enabled;      // GPS enabled flag (0=disabled, 1=enabled)
   uint32_t gps_interval;     // GPS read interval in seconds
   uint8_t autoadd_config;    // bitmask for auto-add contacts config

examples/companion_radio/ui-new/UITask.cpp

@@ -116,6 +116,7 @@ class SettingsScreen : public UIScreen {
     // Sound section
     SECTION_SOUND,
     BUZZER,
+    BUZZER_VOLUME,
     // Radio section
     SECTION_RADIO,
     TX_POWER,
@@ -273,6 +274,14 @@ class SettingsScreen : public UIScreen {
       display.print(_task->isBuzzerQuiet() ? "OFF" : "ON");
 #else
       display.print("N/A");
+#endif
+    } else if (item == BUZZER_VOLUME) {
+      display.print("BzrVol");
+#ifdef PIN_BUZZER
+      renderBar(display, VAL_X, y, _task->getBuzzerVolume() + 1, 5);
+#else
+      display.setCursor(VAL_X, y);
+      display.print("N/A");
 #endif
     } else if (item == TX_POWER) {
       display.print("TX Pwr");
@@ -577,6 +586,14 @@ public:
       _task->toggleBuzzer();  // saves immediately internally
       return true;
     }
+    if (_selected == BUZZER_VOLUME) {
+#ifdef PIN_BUZZER
+      uint8_t lvl = _task->getBuzzerVolume();
+      if (right && lvl < 4) { _task->setBuzzerVolumeLevel(lvl + 1); _dirty = true; return true; }
+      if (left  && lvl > 0) { _task->setBuzzerVolumeLevel(lvl - 1); _dirty = true; return true; }
+#endif
+      return right || left;
+    }
     if (_selected == TX_POWER && p) {
       if (right && p->tx_power_dbm < 22) { p->tx_power_dbm++; _task->applyTxPower(); _dirty = true; return true; }
       if (left  && p->tx_power_dbm > 2)  { p->tx_power_dbm--; _task->applyTxPower(); _dirty = true; return true; }
@@ -2157,6 +2174,7 @@ void UITask::begin(DisplayDriver* display, SensorManager* sensors, NodePrefs* no
 
 #ifdef PIN_BUZZER
   buzzer.quiet(_node_prefs->buzzer_quiet);
+  buzzer.setVolume(_node_prefs->buzzer_volume);
   buzzer.begin();
 #endif
 
@@ -2589,6 +2607,16 @@ void UITask::setBrightnessLevel(uint8_t level) {
   _next_refresh = 0;
 }
 
+void UITask::setBuzzerVolumeLevel(uint8_t level) {
+#ifdef PIN_BUZZER
+  if (_node_prefs == NULL) return;
+  if (level > 4) level = 4;
+  _node_prefs->buzzer_volume = level;
+  buzzer.setVolume(level);
+  _next_refresh = 0;
+#endif
+}
+
 void UITask::toggleBuzzer() {
     // Toggle buzzer quiet mode
   #ifdef PIN_BUZZER

examples/companion_radio/ui-new/UITask.h

@@ -107,6 +107,8 @@ public:
   void applyBrightness();
   void setBrightnessLevel(uint8_t level);
   uint8_t getBrightnessLevel() const { return _node_prefs ? _node_prefs->display_brightness : 2; }
+  void setBuzzerVolumeLevel(uint8_t level);
+  uint8_t getBuzzerVolume() const { return _node_prefs ? _node_prefs->buzzer_volume : 4; }
   void applyTxPower();
   void applyGPSInterval();
   uint32_t autoOffMillis() const {