feat: add community marketplace for custom widgets and CSS

Adds a PocketBase-backed marketplace where users can share custom widgets
and CSS themes. Includes a Docusaurus storefront with GitHub OAuth login,
submission/voting/comments, and a PocketBase SQL view that computes author
names, vote counts, and comment counts without fragile hooks. The Next.js
app gets a modal browser for one-click install from the marketplace plus
clipboard paste-to-import on the custom widgets pages.

apps/docs/src/components/ui/card.tsx

@@ -0,0 +1,70 @@
+import * as React from "react";
+
+import { cn } from "@/lib/utils";
+
+function Card({ className, size = "default", ...props }: React.ComponentProps<"div"> & { size?: "default" | "sm" }) {
+  return (
+    <div
+      data-slot="card"
+      data-size={size}
+      className={cn(
+        "group/card flex break-inside-avoid flex-col gap-(--card-spacing) overflow-hidden rounded-xl bg-card py-(--card-spacing) text-sm text-card-foreground ring-1 ring-foreground/10 [--card-spacing:--spacing(4)] has-data-[slot=card-footer]:pb-0 has-[>img:first-child]:pt-0 data-[size=sm]:[--card-spacing:--spacing(3)] data-[size=sm]:has-data-[slot=card-footer]:pb-0 *:[img:first-child]:rounded-t-xl *:[img:last-child]:rounded-b-xl",
+        className,
+      )}
+      {...props}
+    />
+  );
+}
+
+function CardHeader({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="card-header"
+      className={cn(
+        "group/card-header @container/card-header grid auto-rows-min items-start gap-1 rounded-t-xl px-(--card-spacing) has-data-[slot=card-action]:grid-cols-[1fr_auto] has-data-[slot=card-description]:grid-rows-[auto_auto] [.border-b]:pb-(--card-spacing)",
+        className,
+      )}
+      {...props}
+    />
+  );
+}
+
+function CardTitle({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="card-title"
+      className={cn("font-heading text-base leading-snug font-medium group-data-[size=sm]/card:text-sm", className)}
+      {...props}
+    />
+  );
+}
+
+function CardDescription({ className, ...props }: React.ComponentProps<"div">) {
+  return <div data-slot="card-description" className={cn("text-sm text-muted-foreground", className)} {...props} />;
+}
+
+function CardAction({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="card-action"
+      className={cn("col-start-2 row-span-2 row-start-1 self-start justify-self-end", className)}
+      {...props}
+    />
+  );
+}
+
+function CardContent({ className, ...props }: React.ComponentProps<"div">) {
+  return <div data-slot="card-content" className={cn("px-(--card-spacing)", className)} {...props} />;
+}
+
+function CardFooter({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="card-footer"
+      className={cn("flex items-center rounded-b-xl border-t border-border bg-muted/50 p-(--card-spacing)", className)}
+      {...props}
+    />
+  );
+}
+
+export { Card, CardHeader, CardFooter, CardTitle, CardAction, CardDescription, CardContent };