2d3928ed81
## Problem Reading progress.bin used `SD.exists()` then `SD.open()` without checking if open succeeded. Race conditions or SD errors could cause file handle to be invalid. ## Fix - Removed redundant `SD.exists()` check - Check if file opened successfully before reading - Verify correct number of bytes were read ## Testing - Builds successfully with `pio run` - Affects: `src/activities/reader/EpubReaderActivity.cpp`