Fix widget jumping between monitors (#43) + monitor chooser

[androosio]

Summary

Fixes the widget randomly jumping to the wrong monitor on multi-monitor setups (#43), and adds a way to pick the monitor explicitly.

Fix widget jumping between monitors (#43)

The widget remembered its taskbar by a positional index into a geometry-sorted list. That order is unstable across explorer restarts and display changes, so the index would resolve to the wrong monitor (often a vertical secondary screen) and then get re-saved.

Now the target taskbar is identified by the monitor's stable device name:

• native_interop exposes each taskbar's monitor device name and primary-monitor flag (MonitorFromWindow / GetMonitorInfoW).
• resolve_taskbar_index prefers the remembered monitor, then the primary monitor's taskbar, and only then a positional index — so it no longer defaults to whichever taskbar happens to sort first.
• attach_to_taskbar briefly waits for the remembered monitor's taskbar to come up after an explorer restart instead of falling back immediately.
• Drag-to-another-taskbar records the dropped monitor; Reset position clears the remembered monitor and re-attaches to the primary as an escape hatch.
• taskbar_monitor is persisted in settings.json; old settings without it stay backward compatible.

Monitor chooser

On multi-monitor setups, Settings → Monitor lists each detected taskbar (the primary one is marked) so you can pick which monitor the widget lives on. New menu strings are localized across all 10 languages.

Also adds CLAUDE.md.

Testing

• cargo check / clippy pass for the Windows target.
• Manually verified on a dual-monitor (ultrawide + vertical) setup: the widget stays on the chosen monitor across explorer restarts, and the Monitor / Reset position controls behave as expected.

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