v2.6.2 — PIN entry over the device channel

What's new since v2.6.1

pin_submit over the device channel (v2.6.2)

The 4-digit payment PIN was the last payment-critical step still travelling
over a fresh HTTPS connection — on routers that fail new TLS connections in
phases, the PIN submit could fail exactly while the customer waited at the
PIN pad.

• The channel handler accepts {"event": "pin_submit", "session_id": "...", "pin": "1234"} with the same validation as the HTTPS endpoint and replies
  with pin_submit_result (status / detail) on the same socket
• The HTTPS endpoint POST /api/v1/nfc/pin_submit remains as fallback for
  older firmware and for when the channel is down
• With this, the complete PIN flow rides the persistent channel:
  pin_required and pin_error (via push_to_device() since v2.6.1),
  now also the PIN entry itself

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Compatibility

Combination	Result
PIN-over-channel firmware + extension v2.6.2	✅ intended setup
PIN-over-channel firmware + extension v2.6.1	⚠️ PIN payments fail (PIN sent to channel is ignored, session times out) — plain taps and QR unaffected
Older firmware + extension v2.6.2	✅ PIN arrives via the HTTPS fallback

Component	Required version
LNbits	≥ 1.4.0
ZapBox firmware	PIN-over-channel build (fix/network-stability, commit ab9daca or later) for the full flow

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Upgrade notes

No database migration. Uninstall the old extension in LNbits, install v2.6.2,
flash the matching firmware. Expected log line on the device when a PIN is
entered:

[INFO][PIN] PIN sent over device channel – waiting for WS response