Fix: tabs.tsx data-orientation variants were dead (side-by-side layout)

The shared Tabs primitive used data-horizontal:* / data-vertical:* Tailwind
variants, but the component sets data-orientation='horizontal' (not
data-horizontal). Tailwind v4 data-* variants match attribute names, so
data-horizontal:flex-col on the Tabs root never applied -- the TabsList
and TabsContent laid out side-by-side instead of stacking.

Other consumers (TabbedCard, Settings) wrap their tab children in <div>s,
so the broken flex direction was masked. ServicePage puts TabsList and
TabsContent as direct children of <Tabs>, exposing the bug.

Fix: switch every dead variant to data-[orientation=horizontal]:* /
data-[orientation=vertical]:* (the root flex-col, the list h-8/h-fit/
flex-col, the trigger w-full/justify-start, and the active-indicator
after-element positioning). The full orientation system now works as
intended for both horizontal and vertical tabs.

117 tests pass; lint/build green.

frontend/src/components/ui/tabs.tsx

@@ -14,7 +14,7 @@ function Tabs({
       data-slot="tabs"
       data-orientation={orientation}
       className={cn(
-        "group/tabs flex gap-2 data-horizontal:flex-col",
+        "group/tabs flex gap-2 data-[orientation=horizontal]:flex-col",
         className
       )}
       {...props}
@@ -23,7 +23,7 @@ function Tabs({
 }
 
 const tabsListVariants = cva(
-  "group/tabs-list inline-flex w-fit items-center justify-center rounded-lg p-[3px] text-muted-foreground group-data-horizontal/tabs:h-8 group-data-vertical/tabs:h-fit group-data-vertical/tabs:flex-col data-[variant=line]:rounded-none",
+  "group/tabs-list inline-flex w-fit items-center justify-center rounded-lg p-[3px] text-muted-foreground group-data-[orientation=horizontal]/tabs:h-8 group-data-[orientation=vertical]/tabs:h-fit group-data-[orientation=vertical]/tabs:flex-col data-[variant=line]:rounded-none",
   {
     variants: {
       variant: {
@@ -61,10 +61,10 @@ function TabsTrigger({
     <TabsPrimitive.Trigger
       data-slot="tabs-trigger"
       className={cn(
-        "relative inline-flex h-[calc(100%-1px)] flex-1 items-center justify-center gap-1.5 rounded-md border border-transparent px-1.5 py-0.5 text-sm font-medium whitespace-nowrap text-foreground/60 transition-all group-data-vertical/tabs:w-full group-data-vertical/tabs:justify-start hover:text-foreground focus-visible:border-ring focus-visible:ring-[3px] focus-visible:ring-ring/50 focus-visible:outline-1 focus-visible:outline-ring disabled:pointer-events-none disabled:opacity-50 has-data-[icon=inline-end]:pr-1 has-data-[icon=inline-start]:pl-1 dark:text-muted-foreground dark:hover:text-foreground group-data-[variant=default]/tabs-list:data-active:shadow-sm group-data-[variant=line]/tabs-list:data-active:shadow-none [&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-4",
+        "relative inline-flex h-[calc(100%-1px)] flex-1 items-center justify-center gap-1.5 rounded-md border border-transparent px-1.5 py-0.5 text-sm font-medium whitespace-nowrap text-foreground/60 transition-all group-data-[orientation=vertical]/tabs:w-full group-data-[orientation=vertical]/tabs:justify-start hover:text-foreground focus-visible:border-ring focus-visible:ring-[3px] focus-visible:ring-ring/50 focus-visible:outline-1 focus-visible:outline-ring disabled:pointer-events-none disabled:opacity-50 has-data-[icon=inline-end]:pr-1 has-data-[icon=inline-start]:pl-1 dark:text-muted-foreground dark:hover:text-foreground group-data-[variant=default]/tabs-list:data-active:shadow-sm group-data-[variant=line]/tabs-list:data-active:shadow-none [&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-4",
         "group-data-[variant=line]/tabs-list:bg-transparent group-data-[variant=line]/tabs-list:data-active:bg-transparent dark:group-data-[variant=line]/tabs-list:data-active:border-transparent dark:group-data-[variant=line]/tabs-list:data-active:bg-transparent",
         "data-active:bg-background data-active:text-foreground dark:data-active:border-input dark:data-active:bg-input/30 dark:data-active:text-foreground",
-        "after:absolute after:bg-foreground after:opacity-0 after:transition-opacity group-data-horizontal/tabs:after:inset-x-0 group-data-horizontal/tabs:after:bottom-[-5px] group-data-horizontal/tabs:after:h-0.5 group-data-vertical/tabs:after:inset-y-0 group-data-vertical/tabs:after:-right-1 group-data-vertical/tabs:after:w-0.5 group-data-[variant=line]/tabs-list:data-active:after:opacity-100",
+        "after:absolute after:bg-foreground after:opacity-0 after:transition-opacity group-data-[orientation=horizontal]/tabs:after:inset-x-0 group-data-[orientation=horizontal]/tabs:after:bottom-[-5px] group-data-[orientation=horizontal]/tabs:after:h-0.5 group-data-[orientation=vertical]/tabs:after:inset-y-0 group-data-[orientation=vertical]/tabs:after:-right-1 group-data-[orientation=vertical]/tabs:after:w-0.5 group-data-[variant=line]/tabs-list:data-active:after:opacity-100",
         className
       )}
       {...props}