🔨 Redesign FilledDropdown component to match prototype design

[guiyanakuang]

Closes #3999

Summary

• Replace heavy ExposedDropdownMenuBox + BasicTextField + TextFieldDefaults.DecorationBox with compact Surface trigger + DropdownMenu
• Use rounded rectangle (8dp) with 1dp outline border, consistent with Counter component style
• Compact sizing: 13sp font, 14dp chevron icon, minimal padding
• Fix hover/ripple shape clipped to rounded corners via Modifier.clip()
• Set containerColor and shape on DropdownMenu to match trigger, eliminating edge color mismatch
• Compact menu items with fixed 32dp height and matching content padding
• Selected item indicated by primary-colored text + check icon
• Replace manual text width measurement with intrinsic sizing
• Use AppUISize constants throughout

Test plan

• Verify dropdown trigger renders with rounded rectangle and border
• Verify hover/ripple clips to rounded corners
• Verify dropdown menu background matches trigger (no edge color mismatch)
• Verify menu items are compact and visually consistent with trigger
• Verify selection works and selected item shows primary text + check icon