Adds a "2. CONFIGURATION" step alongside WiFi setup: a second QR code
linking straight to the captive portal page (http://<ap-ip>/), for anyone
who's joined the AP but wants a one-scan shortcut to the config form
instead of relying on the captive-portal popup. The AP netif is now
created (but not started) before the display renders, since the AP's IP
is fixed at netif creation and needed for this QR before the network is
actually up.
Pulls the pixel/text drawing primitives (previously private to
qr_onboarding.c) out into epd_draw.c/.h so the upcoming status screen can
reuse them instead of duplicating.
Vendors two small MIT/BSD-3-Clause libraries rather than hand-rolling
either: Nayuki's qrcodegen (QR matrix generation) and Waveshare's Font24
bitmap table from their e-Paper repo (same repo the epd7in3e driver came
from) for rendering readable text on the panel.
qr_onboarding_show() builds a standard WIFI:T:WPA;S:...;P:...;; payload,
rasterizes the QR module matrix plus the SSID and password as plaintext
underneath (for anyone provisioning from a device that can't scan a QR)
onto a malloc'd frame buffer, and pushes it to the panel via
epd_display_buffer(). The buffer is heap-allocated on demand rather than
statically reserved, since 192KB held permanently in BSS would eat into
the RAM budget the HTTP fetch path (task 6) is specifically trying to keep
free.
Wired into wifi_provisioning_start() before the softAP comes up, so the
join instructions are already on-screen by the time the network is
joinable.
tfaour