refactor(frontend): restructure project layout and update API schema

Relocate frontend source code from `next-app/` to `frontend/` to align with the new project structure. This includes removing the old Next.js boilerplate files and establishing a cleaner workspace.

Additionally, updates the OpenAPI specification to include support for the `immich` widget type and its corresponding configuration schema.

- Move frontend files to `frontend/`
- Delete obsolete `next-app/` directory and its configuration
- Add `immich` widget type to `openapi.yaml`
- Update `FrontendPlan.md` with dashboard refactor and UX direction

frontend/components/ui/scroll-area.tsx

@@ -0,0 +1,41 @@
+"use client";
+
+import * as React from "react";
+import * as ScrollAreaPrimitive from "@radix-ui/react-scroll-area";
+import { cn } from "@/lib/utils";
+
+const ScrollArea = React.forwardRef<
+  React.ComponentRef<typeof ScrollAreaPrimitive.Root>,
+  React.ComponentPropsWithoutRef<typeof ScrollAreaPrimitive.Root>
+>(({ className, children, ...props }, ref) => (
+  <ScrollAreaPrimitive.Root ref={ref} className={cn("relative overflow-hidden", className)} {...props}>
+    <ScrollAreaPrimitive.Viewport className="h-full w-full rounded-[inherit]">
+      {children}
+    </ScrollAreaPrimitive.Viewport>
+    <ScrollBar />
+    <ScrollAreaPrimitive.Corner />
+  </ScrollAreaPrimitive.Root>
+));
+ScrollArea.displayName = ScrollAreaPrimitive.Root.displayName;
+
+const ScrollBar = React.forwardRef<
+  React.ComponentRef<typeof ScrollAreaPrimitive.ScrollAreaScrollbar>,
+  React.ComponentPropsWithoutRef<typeof ScrollAreaPrimitive.ScrollAreaScrollbar>
+>(({ className, orientation = "vertical", ...props }, ref) => (
+  <ScrollAreaPrimitive.ScrollAreaScrollbar
+    ref={ref}
+    orientation={orientation}
+    className={cn(
+      "flex touch-none select-none transition-colors",
+      orientation === "vertical" && "h-full w-2.5 border-l border-l-transparent p-[1px]",
+      orientation === "horizontal" && "h-2.5 flex-col border-t border-t-transparent p-[1px]",
+      className,
+    )}
+    {...props}
+  >
+    <ScrollAreaPrimitive.ScrollAreaThumb className="relative flex-1 rounded-full bg-border" />
+  </ScrollAreaPrimitive.ScrollAreaScrollbar>
+));
+ScrollBar.displayName = ScrollAreaPrimitive.ScrollAreaScrollbar.displayName;
+
+export { ScrollArea, ScrollBar };