🎨 Palette: Add ARIA state to custom dropdown toggles

[endlessblink]

💡 What: Added aria-expanded and aria-haspopup attributes to the trigger buttons for custom dropdown menus in QuickTaskDropdown.vue and CalendarHeader.vue.
🎯 Why: Screen reader users need to know if a button opens a dialog/menu and what its current expanded state is. This allows assistive technologies to announce the dropdown's state correctly.
📸 Before/After: No visual changes.
♿ Accessibility: Improves custom component compatibility with screen readers by adhering to ARIA guidelines for custom popovers.

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PR created automatically by Jules for task 4005737871893870453 started by @endlessblink

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