Adds a "Pair" frame, shown while Bluetooth is enabled, with a centered QR
code of meshtastic://meshtastic/connections?address=x<BLE MAC>[&pin=<PIN>].
The PIN is included in FIXED_PIN and RANDOM_PIN modes: the random PIN is
picked once when Bluetooth starts, so it is known before pairing begins.
NRF52Bluetooth and NimbleBluetooth gain getPasskey() to report it. The PIN
is not printed on the frame.
The encoder (src/graphics/QrEncode.cpp) is a cut-down ricmoo/QRCode:
ECC level M, versions 1-6, byte mode, with function modules computed
instead of tracked in a second grid. About 2.7 KB of flash and ~200 B of
stack while encoding. The 73-character link encodes as version 5
(37x37), which fits a 128x64 panel at one pixel per module.
test_qr_encode pins the link's symbol against Project Nayuki's encoder
and checks version selection at each capacity boundary.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011C7D9bSthe6aUpG3jEHLyt
