V2: Per-country year ranges

[Nielsvanpach]

Summary

• Remove the global 1970–2037 year restriction from Country::ensureYearCanBeCalculated()
• Add supportedYearRange() method to Country (returns null = unlimited by default)
• 9 countries with calendar lookup tables declare their actual supported ranges (e.g. Albania 2024–2034, Turkey 1970–2037)
• ~70 countries with only fixed/Easter-based holidays now support any year
• ResolvesCalendarDates error messages now derive min/max from the actual lookup data instead of hardcoding 1970/2037

Breaking changes

• Countries without lookup tables no longer throw for years outside 1970–2037
• Error messages changed from "Holidays can only be calculated for years after/before X" to "Only years between X and Y are supported for {countryCode}"