fix(calendar) calendar selected day border radius & date range picker selection start border radius

[anatolzak]

Fixed border radius of selected day in calendar of default theme

before (you might need to zoom in to see the dark corners) https://ui.shadcn.com/docs/components/calendar

after

Fixed border radius of selection start in date range picker in default theme

before (you might need to zoom in to see the dark corners) https://ui.shadcn.com/docs/components/date-picker#date-range-picker

after

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[hakan-akgul]

I tested the PR. Works well 🚀