feat(wio-tracker-l2): internal flash as LittleFS instead of SPIFFS

helpers/esp32/InternalFS.h picks the filesystem: -D ESP32_LITTLEFS mounts
LittleFS on the same "spiffs" partition, otherwise SPIFFS as before. Only the
L2 LVGL envs set it; every other ESP32 board is unchanged. A settings save
drops from ~0.5 s to ~80 ms and the files survive power loss mid-write.
No migration: the first boot formats the partition (fresh identity).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

examples/companion_radio/DataStore.cpp

@@ -81,7 +81,7 @@ void DataStore::begin() {
 }
 
 #if defined(ESP32)
-  #include <SPIFFS.h>
+  #include <helpers/esp32/InternalFS.h>
   #include <nvs_flash.h>
 #elif defined(RP2040_PLATFORM)
   #include <LittleFS.h>
@@ -119,7 +119,7 @@ lfs_ssize_t _getLfsUsedBlockCount(FILESYSTEM* fs) {
 
 uint32_t DataStore::getStorageUsedKb() const {
 #if defined(ESP32)
-  return SPIFFS.usedBytes() / 1024;
+  return ESP32_FS.usedBytes() / 1024;
 #elif defined(RP2040_PLATFORM)
   FSInfo info;
   info.usedBytes = 0;
@@ -137,7 +137,7 @@ uint32_t DataStore::getStorageUsedKb() const {
 
 uint32_t DataStore::getStorageTotalKb() const {
 #if defined(ESP32)
-  return SPIFFS.totalBytes() / 1024;
+  return ESP32_FS.totalBytes() / 1024;
 #elif defined(RP2040_PLATFORM)
   FSInfo info;
   info.totalBytes = 0;
@@ -198,7 +198,7 @@ bool DataStore::formatFileSystem() {
 #elif defined(RP2040_PLATFORM)
   return LittleFS.format();
 #elif defined(ESP32)
-  bool fs_success = ((fs::SPIFFSFS *)_fs)->format();
+  bool fs_success = ((ESP32_FS_CLASS *)_fs)->format();
   esp_err_t nvs_err = nvs_flash_erase(); // no need to reinit, will be done by reboot
   return fs_success && (nvs_err == ESP_OK);
 #elif defined(SIM_PLATFORM)