Remove the call to loadAllFileStatSlims() which pre-loads all ZIP central
directory entries into memory. For EPUBs with 2000+ chapters (like webnovels),
this exhausts the ESP32-C3's ~380KB RAM and causes abort().
The existing loadFileStatSlim() function already handles individual lookups
by scanning the central directory per-file when the cache is empty. This is
O(n*m) instead of O(n), but prevents memory exhaustion.
Fixes#134
481b8210fb