Add software LiPo UV protection with energy-save boot.

Detect under-voltage on GPIO1/11, persist UV state in NVS, enter a minimal
power mode without ESP-NOW, and recover after charge; expose LED mode 6
battery-low for host testing via goTool.

Co-authored-by: Cursor <cursoragent@cursor.com>

main/powerpod.c

@@ -31,6 +31,7 @@
 #include "led_ring.h"
 #include "pod_settings.h"
 #include "uart.h"
+#include "battery_uv.h"
 #include <stdint.h>
 
 enum MASTER_STATES {
@@ -78,6 +79,16 @@ void app_main(void) {
     ESP_LOGW(TAG, "settings NVS init failed; using defaults");
   }
 
+  if (board_input_init_adc_only() != ESP_OK) {
+    ESP_LOGW(TAG, "LiPo ADC init failed");
+  }
+
+#if POWERPOD_BATTERY_UV_ENABLE
+  if (battery_uv_evaluate_boot()) {
+    battery_uv_run_mode();
+  }
+#endif
+
   // Get Master Mode Pin
   gpio_reset_pin(DIP_MASTER);
   gpio_set_direction(DIP_MASTER, GPIO_MODE_INPUT);
@@ -167,7 +178,8 @@ void app_main(void) {
   ESP_LOGI(TAG, "Running Partition: %s (OTA slot %d)",
            app_config.running_partition, ota_slot);
 
-  board_input_init();
+  board_input_start_lipo_monitor();
+  board_input_init_button();
 
   err = esp_now_comm_init(&app_config);
   if (err != ESP_OK) {