feat: add EP29Rv2_128x296 2.9" B/W/R panel (GDEM029C90, SSD1680)

[grzegorzpuk-cpu]

Add EP29Rv2_128x296: 2.9" 128x296 B/W/R (GDEM029C90, SSD1680)

Summary

Adds a new panel type EP29Rv2_128x296 for the 2.9" 128x296 Black/White/Red
e-paper display (GoodDisplay GDEM029C90, SSD1680 controller). The init
sequence follows the proven GxEPD2 GxEPD2_290_C90c driver, which drives the
same panel correctly.

This is a purely additive change: the existing EP29R_128x296 and
EP26R_152x296 entries are left untouched.

Changes

src/bb_epaper.h

• New enum value EP29Rv2_128x296 added just before EP_PANEL_COUNT.

src/bb_ep.inl

1. New init sequence epd29rv2_init_sequence_full, matching
   GxEPD2_290_C90c::_InitDisplay():
   • 0x21 (Display Update Control 1) sent with 2 data bytes
     (0x00, 0x80) — the SSD1680 expects 2 bytes here; sending only 1
     desynchronises the rest of the init sequence
   • 0x3C border waveform = 0x05
   • RAM X end = 0x0F (128 px), RAM Y end = 0x0127 (296 rows)
   • RAM Y counter starts at 0
2. New panelDefs[] entry:
   {128, 296, 0, epd29rv2_init_sequence_full, NULL, NULL, BBEP_3COLOR, BBEP_CHIP_SSD16xx, u8Colors_3clr}
3. bbepRefresh(): special case for EP29Rv2_128x296 using display update
   control value 0xF7 (full LUT refresh, same as GxEPD2_290_C90c
   _Update_Full()), instead of the default 3-color 0xC7.

Why not reuse EP29R_128x296?

EP29R_128x296 exists but its init sequence has issues on this panel:

• 0x21 sent with only 1 data byte (SSD1680 requires 2)
• master activation (0x20) commented out
• RAM Y counter initialised to the last row instead of 0

Those are left as-is to avoid regressions for anyone currently using
EP29R_128x296; the new panel type provides a correct, tested path for
GDEM029C90.

Tested

• Hardware: WeAct Studio ESP32-C3 + 2.9" 128x296 B/W/R panel (GDEM029C90)
• Pins: CS=7, DC=9, RES=8, BUSY=5, MOSI=6, SCLK=4
• Full-screen black/white/red fills: correct, no Y offset, no garbage rows
• Alternating black/red text lines across the whole display: correct
• Text + circles + bitmap (three_color example content, rotation 270): correct

Usage

BBEPAPER bbep(EP29Rv2_128x296);

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