v1.10.13-alpha.1 — multi-device BKW command routing (test build)

🧪 Experimental: multi-device BKW main-SN command routing (#48)

Per the official EcoFlow STREAM/BKW docs, in a multi-device BKW system every control command must be sent to the main (master) device SN. This build resolves it automatically and routes commands there.

How it works (two-SN model):

• On setup, resolves the main SN via GET /iot-open/sign/device/system/main/sn?sn=<configured> (STREAM/BKW device types only).
• Command SN (main) → MQTT /set + /set_reply topics and the REST write.
• State SN (configured) → /quota + /status (state is read from the device you added).
• Single-device systems and any resolution failure fall back to the configured SN — no behavior change.

Affected controls: AC1/AC2 switches, Backup Reserve, Operating Mode, Feed-in, Base Load Power.

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🧪 Pre-release / testing build, off v1.10.12. This is largely defensive doc-compliance and could not be verified locally (no multi-device hardware). The goal is to confirm no regression on existing single-/master-device setups; multi-device confirmation is very welcome.

Scope limit: command routing only. If you added a non-main device that does not report relay state, AC switches still won't appear (unchanged).

@esserandreas89-maker @BaBateck — testing this would be hugely helpful. Please report whether AC1/AC2, backup reserve, and feed-in commands succeed (no error 8524), and whether the needAck MQTT path works (set_reply received).