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/label.tsx

@@ -0,0 +1,19 @@
+"use client";
+
+import * as React from "react";
+import * as LabelPrimitive from "@radix-ui/react-label";
+import { cn } from "@/lib/utils";
+
+const Label = React.forwardRef<
+  React.ComponentRef<typeof LabelPrimitive.Root>,
+  React.ComponentPropsWithoutRef<typeof LabelPrimitive.Root>
+>(({ className, ...props }, ref) => (
+  <LabelPrimitive.Root
+    ref={ref}
+    className={cn("text-xs font-medium leading-none peer-disabled:cursor-not-allowed peer-disabled:opacity-70", className)}
+    {...props}
+  />
+));
+Label.displayName = LabelPrimitive.Root.displayName;
+
+export { Label };