Two related fixes that together let the post-WiFi-setup window be quiet:
1. operation.h 204/404: skip the panel redraw entirely. The panel already
holds the right thing — setup QR if no image has ever been painted
(img_id == -1), or a real photo if img_id >= 0. Redrawing the QR every
15s during the bootstrap claim window put the e-ink into a perpetual
~20s mid-refresh loop and risked ghosting. Tests updated to assert
no redraw on either sub-case.
2. main.cpp WiFi-fail path: drop the epd_fill(RED) + 3s delay + AP
re-redraw sequence (~43s of e-ink work that destroyed the QR mid-flow)
and replace with a single repaint of a new "Connection Failed — try
again" Step 1/2 screen with red accents. gen_screens.py grows a
gen_ap_retry() variant that recolors yellow → red and swaps the
header/QR labels; the result is shipped as ap_bg_retry.bin alongside
ap_bg.bin in LittleFS. epd.h exposes epd_draw_ap_screen_retry().
