Graph widgets need consistent value scaling (kB/MB/GB, kbps/Mbps, …). Add
shared `unit` (none/bytes/bytes_per_sec/bits_per_sec/bits/percent/seconds) and
`scale` (auto/k/m/g/t) enum fields to:
- PrometheusChartWidgetConfig (alongside promql/window)
- new QbittorrentSpeedWidgetConfig — the speed widget previously had NO config
options at all; totals/active keep their empty config.
Declared as Pydantic Literal enums so the widget-kind JSON schema exposes
`enum`, which the frontend config dialog renders as a dropdown. The data
sources are unchanged (raw values); scaling is a display concern handled
client-side. qBittorrent speed defaults to bytes/sec.
Test: chart widget kinds expose the shared unit/scale enums; speed defaults to
bytes_per_sec; totals/active stay option-less. 389/389 backend tests pass.
Developer
05a9faca3e