refactor(frontend): ui-components on tailwind-variants

[Kadrian]

Third step of the emotion → tailwind migration: src/js/ui-components/** (27 files) is emotion-free.

• inputs, selects, multi-select, date pickers, dropzones, toggles, editable text/tags, import modal: every styled() is a tv() now, flags → variants, precedence of conflicting flags encoded by variant order (commented)
• InputSelectComponents exports stay, as small components taking className + the same flags; downshift props/refs still spread through
• react-datepicker internals (InputDate) styled via a scoped .conquery-datepicker block in index.css, calendarContainer override dropped
• DropzoneWithFileInput: the shouldForwardProp shim from refactor(frontend): button and icon components on tailwind-variants #3985 is gone, outside is a variant
• emotion hid raw elements from biome's a11y rules: ToggleButton options are <button>s now; Dropzone, InputCheckbox, CustomHeader's month/year label and InputDate's escape handler keep their div onClick with biome-ignore + TODO
• SelectListOption: disabled no longer lands as a DOM attribute on the div (was never functional)
• Input's disabled placeholder opacity now applies (old selector had a typo &:placehoder)