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/lib/pocketbase.ts

@@ -0,0 +1,52 @@
+import PocketBase from "pocketbase";
+
+let client: PocketBase | undefined;
+let clientUrl: string | undefined;
+
+export const getPocketBase = (url: string): PocketBase => {
+  if (!client || clientUrl !== url) {
+    client = new PocketBase(url);
+    clientUrl = url;
+  }
+  return client;
+};
+
+export const getSubmissionFileUrl = (baseUrl: string, submissionId: string, filename: string) =>
+  `${baseUrl}/api/files/submissions/${submissionId}/${filename}`;
+
+export interface StoreSubmission {
+  id: string;
+  collectionId: string;
+  collectionName: string;
+  type: "css" | "widget";
+  title: string;
+  description: string;
+  schemaVersion: string;
+  content: string;
+  screenshots: string[];
+  upvotes: number;
+  downvotes: number;
+  commentCount: number;
+  version: number;
+  changelog: string;
+  author: string;
+  authorName: string;
+  created: string;
+}
+
+export interface StoreVote {
+  id: string;
+  submission: string;
+  user: string;
+  value: 1 | -1;
+}
+
+export interface StoreComment {
+  id: string;
+  submission: string;
+  author: string;
+  content: string;
+  created: string;
+  updated: string;
+  expand?: { author?: { id: string; name?: string; username?: string } };
+}