Add companion OTA and configurable Zigbee nodes

[fellpower]

Problem and resulting behavior

The upstream firmware has no complete field-update path for the Tab5 companion controllers and no Tab5-managed external Zigbee I/O node. This draft adds guarded OTA workflows for the internal C6, ESP32-S3 bridge and NanoH2, plus a configurable external ESP32-C6 Zigbee Node.

A user can now update companion firmware from the Tab5, pair and retain an external Zigbee Node, configure its name/status LED/channels, and use switch, digital input/output and DS18B20 channel types without direct access to the installed controller.

Main changes

• Add guarded Tab5 OTA flows for Internal C6, S3 bridge and NanoH2.
• Support ESP-Hosted factory 1.4.1 and current 2.11.4 C6 update behavior.
• Add ESP-NOW S3 discovery, liveness tracking, automatic reconnect and remotely stored board/UART settings.
• Add NanoH2 UART OTA while keeping the Tab5 UI responsive during transfer.
• Add the external Modulus Zigbee Node ESP32-C6 firmware.
• Configure node name, status LED GPIO/polarity and up to twelve channels from the Tab5.
• Support switch, digital output, digital input and DS18B20 endpoints.
• Persist Zigbee radio, pairing and node configuration across restarts.
• Improve the M Panel Zigbee and firmware-update interfaces.
• Add reproducible build and local port helper scripts.

Validation

• Zig test suite: 520 tests, successful.
• Zigbee Node host tests: temperature decoding/CRC/range, GPIO conflicts, persistence and schema migration pass.
• Internal C6 factory 1.4.1 -> ESP-Hosted 2.11.4 OTA tested on a physical Tab5.
• NanoH2 OTA tested through the Tab5; verification/restart completes and the UI remains responsive.
• External ESP32-C6 node pairing, retained reconnect, configurable GPIO and status LED tested.
• Seeed XIAO ESP32-S3 discovery and connection tested.
• Generic QFN56 ESP32-S3 full image flashed and successfully discovered/connected by the Tab5 ESP-NOW scan.

Still to validate before marking ready

• Physical relay-board switching through the external node driver stage.
• Physical DS18B20 sensor readings and disconnect/reconnect behavior.
• Final release packaging and user documentation review.

This is intentionally a draft because the branch spans the complete OTA/Zigbee feature set and the remaining hardware acceptance tests have not yet been completed.