feat: forward device LOG_INFO to syslog endpoint on Pi5 bridge

[Strycher]

Goal

Centralize device logs on the Pi5 bridge so failures can be diagnosed after the fact without USB serial, and so multiple devices' logs sit side-by-side on one host.

Motivation

`Logger::logPrintf` writes to SD on-device, which survives reboot but requires:

• Pulling the SD card physically, OR
• Browsing the existing web-serial endpoint device-by-device

Centralized syslog-style ingestion solves both. Multiple devices' logs are queryable together. Standard ops pattern.

Proposed shape

• Bridge side: new endpoint `POST /api/device/log` accepting batched `{device_id, lines: [{ts, level, msg}, ...]}` JSON. Persists to a rotating log file (`/app/data/device-logs/.log`) or forwards to host syslog. Configurable retention.
• Device side: new module that subscribes to `Logger` output, buffers in a FreeRTOS queue (drop-oldest on overflow so it never blocks the logging caller), batches every N seconds OR M lines, POSTs to the bridge. Robust against transient network failures (drop or backpressure, don't crash).
• Failure mode: if bridge endpoint is down, queue fills to a cap and oldest entries get dropped. Device logs continue going to SD card uninterrupted. Centralization is best-effort, not gating.

Notes

• Both DCC devices (dcc-panel7, dcc-desk) and potentially other DW devices over time
• Should NOT block the calling task — logging must remain non-blocking
• Format compatible with standard syslog parsers preferred (RFC 5424-ish if cheap; otherwise plain JSONL)