feat(ui): touch-size controls, scrollable dialogs, motion levels everywhere, load states

- Inputs and selects are 44 px on phones (36 px from sm up); default and
  small buttons get 40/36 px on phones.
- Dialogs scroll inside the viewport, so long edit forms keep their
  save button reachable on a phone.
- Dialog zoom, sheet slide, sidebar icon scale and stat-bar growth only
  move at the motion level "Voll" (motion-full), not at "Dezent".
- QueryState / ErrorState / LoadingState: loading, error with "Erneut
  versuchen", empty, data - a failed load can no longer look like an
  empty list. EmptyState takes an action for the obvious next step.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

ApiCore-Frontend/src/app/(app)/sidebar.tsx

@@ -142,7 +142,7 @@ function SidebarLink({ item, pathname }: { item: NavItem; pathname: string }) {
       <Icon
         className={cn(
           "size-4.5 shrink-0 transition-transform duration-150",
-          !isActive && "group-hover:scale-110",
+          !isActive && "motion-full:group-hover:scale-110",
         )}
       />
       <span className="truncate">{item.label}</span>