Multi-day forecast pane

[PhillyUrbs]

Summary

Show the next 2–3 days of forecast in addition to today, so the user can plan an outfit for the week.

Why

Open-Meteo already returns a 7-day forecast. We currently use only forecast_days=1 and show today's hi/lo. A small horizontal strip with 'Tomorrow' and 'Day after' icons + hi/lo would massively improve usefulness for outfit planning.

Proposed approach

• Bump forecast_days to 3 in outfitpi/weather.py.
• Extend CurrentWeather (or add a Forecast dataclass) with the additional days.
• Add a small forecast strip below the today card on the dashboard. On 800x480 portrait, it lives between weather and the kids panes; on landscape it tucks into the right column.
• Don't drive recommendations from these — they're informational only.
• Toggle in Settings to hide if the user prefers the simpler current view.

Acceptance criteria

• Settings toggle: Show 3-day forecast (default on).
• Layout works at 800x480 in both orientations and at phone widths.
• Cached weather still serves the multi-day data when offline.
• Tests cover the new dataclass fields and the parse logic.

Tracked: was item #8 from the GitHub-features brainstorm.

[PhillyUrbs]

Note: superseding #8 (forecast-day navigation arrows). The strip approach here is the primary direction, but if deep navigation is wanted later we can layer arrow-based per-day browsing on top.