MagTag SSD1680: GxEPD2_4G LUT, reset fix, unify 0x44+0xca

- Pulse RESET low before User ID read so SSD1680 wakes from deep sleep
- Replace ad-hoc LUT with GxEPD2_4G reference (VS L0↔L3 swapped, 0x48 DC balance)
- VCOM=0x24 empirically tuned for FPC-7519rev.b contrast
- Both 0x44 (FPC-7619rev.b) and 0xca (FPC-7519rev.b) share the same sequence

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>