Added 3 new config fields to price trend options step:
- Trend Change Confirmation (2-6 intervals slider)
- Min Price Change for trend (display-unit-aware slider)
- Min Price Change for strong trend (display-unit-aware slider)
Price change sliders scale between base currency (EUR/NOK) storage and
display unit (ct/øre) presentation using get_display_unit_factor().
Added migration in __init__.py to convert old display-unit values to
base currency format.
Impact: Users can tune trend sensitivity: higher confirmation = fewer
false changes, higher min price change = no trends from tiny fluctuations.
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