Use smaller files on the SD card

[beastoin]

The larger an SD card file is, the slower the read/write access becomes, and the more battery it consumes.

The current firmware writes one large file to the SD card when the device is disconnected, which leads to significant battery consumption.

Key results:

• Firmware: When the device is disconnected, write smaller, time-based files (e.g., 5-minute audio chunks) instead of one large file. Each file name must contain a timestamp.
• App: Sync the audio files according to these smaller file chunks.

Refs:

• Related Issue: Make sure 250mah (current charge on DK2) is enough for 4 days of use with no charge #1508

• Firmware sdcard.c, storage.c : https://github.com/BasedHardware/omi/blob/main/Friend/firmware/firmware_v1.0/src/sdcard.c , https://github.com/BasedHardware/omi/blob/main/Friend/firmware/firmware_v1.0/src/storage.c

• App's SD card's Sync: https://github.com/BasedHardware/omi/blob/main/app/lib/services/wals.dart#L148

• Writes one large file's battery consumption:

  

• Writes small files's battery consumption: