De-template the frontend and apply the design system

- FastAPI branding replaced throughout: title, favicon, logo (now the org/
  brand SVGs), footer links, route titles; workspace package renamed
- shadcn primitives restyled to the component radius/shadow map: pill
  controls, rounded-lg surfaces, shadow-e1/e2/e3
- floating frosted AppSidebar over a bg-card content region
- theme storage key aligned with the pre-paint script, MotionConfig added
- scripts/capture-screenshots.mjs backs the root 'make verify'

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

frontend/src/components/ui/sidebar.tsx

@@ -254,7 +254,7 @@ function Sidebar({
         <div
           data-sidebar="sidebar"
           data-slot="sidebar-inner"
-          className="bg-sidebar group-data-[variant=floating]:border-sidebar-border flex h-full w-full flex-col group-data-[variant=floating]:rounded-lg group-data-[variant=floating]:border group-data-[variant=floating]:shadow-sm"
+          className="bg-sidebar group-data-[variant=floating]:border-sidebar-border flex h-full w-full flex-col group-data-[variant=floating]:rounded-lg group-data-[variant=floating]:border group-data-[variant=floating]:shadow-e1"
         >
           {children}
         </div>
@@ -321,7 +321,7 @@ function SidebarInset({ className, ...props }: React.ComponentProps<"main">) {
       data-slot="sidebar-inset"
       className={cn(
         "bg-transparent relative flex w-full flex-1 flex-col",
-        "md:peer-data-[variant=inset]:m-2 md:peer-data-[variant=inset]:ml-0 md:peer-data-[variant=inset]:rounded-xl md:peer-data-[variant=inset]:shadow-sm md:peer-data-[variant=inset]:peer-data-[state=collapsed]:ml-2",
+        "md:peer-data-[variant=inset]:m-2 md:peer-data-[variant=inset]:ml-0 md:peer-data-[variant=inset]:rounded-lg md:peer-data-[variant=inset]:shadow-e1 md:peer-data-[variant=inset]:peer-data-[state=collapsed]:ml-2",
         className,
       )}
       {...props}
@@ -496,7 +496,7 @@ const sidebarMenuButtonVariants = cva(
       size: {
         default: "h-8 text-sm rounded-lg",
         sm: "h-7 text-xs",
-        lg: "h-12 text-sm group-data-[collapsible=icon]:p-0! rounded-xl data-[state=closed]:rounded-lg",
+        lg: "h-12 text-sm group-data-[collapsible=icon]:p-0! rounded-lg data-[state=closed]:rounded-lg",
       },
     },
     defaultVariants: {