fix: accept forecast arrays in widget decoder

[naltatis]

pairs with evcc-io/evcc#32391, replaces the format from evcc-io/evcc#31765

evcc is switching the forecast payload from {start, end, value} objects with RFC3339 strings to [start, end, value] arrays with unix seconds, and the solar timeseries from {ts, val} to [ts, val]. The widget decoder now accepts both, so widgets keep working across old and new evcc versions.

• ForecastSlot and SolarPoint decode from an unkeyed container first, falling back to the keyed object form
• the date decoding strategy still accepts RFC3339 strings and unix seconds, covering the object form from either evcc version

🤖 Generated with Claude Code

[andig]

@naltatis can we merge this? Should support both formats.

[naltatis]

Verified both versions working on iOS devices.

[andig]

Why is this even relevant for the app? Because it displays the forecast in its widget?

[naltatis]

Yes. The widgets call the API directly. You cant run a browser there. Widget-runtime is quite restricted.