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/main.cpp

@@ -54,8 +54,8 @@ static uint32_t _atoi(const char* sp) {
   #include <LittleFS.h>
   DataStore store(LittleFS, rtc_clock);
 #elif defined(ESP32)
-  #include <SPIFFS.h>
-  DataStore store(SPIFFS, rtc_clock);
+  #include <helpers/esp32/InternalFS.h>
+  DataStore store(ESP32_FS, rtc_clock);
 #elif defined(SIM_PLATFORM)
   #include <SimFS.h>
   // Real files under ./sim_data/ (relative to the process's cwd) so
@@ -271,7 +271,7 @@ void setup() {
   #endif
     the_mesh.startInterface(serial_interface);
 #elif defined(ESP32)
-  SPIFFS.begin(true);
+  ESP32_FS.begin(true);
   store.begin();
   the_mesh.begin();
   resolveBLEPin(