Defer BLE-callback display teardown and MSD update to the main loop (ESP32)

[balloob]

Summary

On ESP32, onConnect() and onDisconnect() run in the BLE host task, but they performed work that races the Arduino loop() task:

• onConnect() called updatemsdata() — I2C sensor reads and mutation of shared MSD/advertising state — concurrently with the same work in loop().
• onDisconnect() called cleanupDirectWriteState(true) — bbepSleep / SPI.end() / Wire.end() / pwrmgm(false) — while loop() may be mid bbepWriteData on the same SPI bus during a direct-write upload (the epdRefreshInProgress guard only covers the refresh phase, not the upload phase). That powers the panel down under an in-flight transfer and clears state the handler is still using.

Fix

Set pending flags in the callbacks and perform the work in loop(), mirroring the existing bleRestartAdvertisingPending deferral: onConnect sets bleConnectMsdUpdatePending, onDisconnect sets bleDirectWriteCleanupPending, and loop() acts on them right after the advertising-restart handling.

Verification

• Compiled clean (not flashed) for esp32-N4 and nrf52840custom.

⚠️ Needs on-hardware testing. This changes concurrency timing on ESP32. Please verify: (1) connecting refreshes the MSD/advertisement as before; (2) disconnecting during a direct-write image upload cleanly aborts and powers the panel down without a crash or bus fault; (3) a normal image upload + refresh still completes. Note this touches the same onDisconnect block as #56 (touch-suspend), so the two will need a trivial merge.