chore: general repo maintenance and docs cleanup (#3030)

Refresh README/docs for the current stack, add a security policy,
note the external-PR pause, and remove dead config and workflows.

apps/docs/content/docs/developers/local-development/index.mdx

@@ -15,16 +15,17 @@ Pick the one that fits your needs the best.
 
 ## Tech Stack
 
-- [Typescript](https://www.typescriptlang.org/) - Language
-- [React Router](https://reactrouter.com/) - Framework
+- [TypeScript](https://www.typescriptlang.org/) - Language
+- [React Router v7](https://reactrouter.com/) - Framework
+- [Hono](https://hono.dev/) - Server
 - [Prisma](https://www.prisma.io/) - ORM
-- [Tailwind](https://tailwindcss.com/) - CSS
-- [shadcn/ui](https://ui.shadcn.com/) - Component Library
+- [Tailwind CSS](https://tailwindcss.com/) - CSS
+- [shadcn/ui](https://ui.shadcn.com/) + [Radix UI](https://www.radix-ui.com/) - Component Library
 - [react-email](https://react.email/) - Email Templates
+- [Lingui](https://lingui.dev/) - Internationalization
 - [tRPC](https://trpc.io/) - API
-- [@documenso/pdf-sign](https://www.npmjs.com/package/@documenso/pdf-sign) - PDF Signatures
-- [React-PDF](https://github.com/wojtekmaj/react-pdf) - Viewing PDFs
-- [PDF-Lib](https://github.com/Hopding/pdf-lib) - PDF manipulation
+- [@libpdf/core](https://www.npmjs.com/package/@libpdf/core) - PDF Signing and Manipulation
+- [pdf.js](https://mozilla.github.io/pdf.js/) - Viewing PDFs
 - [Stripe](https://stripe.com/) - Payments
 
 <div className="mt-16 flex items-center justify-center gap-4">