Fix month/year dropdown layout, add minDate/maxDate

[iamganeshkarki]

Fix month/year dropdown layout, add minDate/maxDate, keyboard + ARIA support

• Fix month and year dropdowns being independently toggleable, which let both stay open at once; state is now lifted to CalenderController so opening one closes the other.
• Fix header row layout: prev/next icons were pushed to the popup's far edges by justify-content: space-between, ending up far from the month/year controls; now grouped together with a fixed popup width so content doesn't overflow, capped for narrow/mobile viewports.
• Re-enable the year dropdown's scroll-to-selected-year behavior (was dead/commented-out code), so opening it for an old date doesn't dump you at the top of a 130-year list.
• Add minDate/maxDate props (AD date strings) that disable out-of-range days and the month navigation that would lead to them.
• Add keyboard support (Enter/Space to activate, Escape to close and refocus the input) and ARIA attributes across the input, month/year triggers, dropdown options, day cells, and prev/next/today controls.
• Convert prev/next/today controls from non-interactive to real elements for native keyboard operability.