refactor: migrate documentation to support multi-language structure with i18n integration

documentation/content/docs/stack/index.mdx

@@ -0,0 +1,17 @@
+---
+title: Tech Stack
+description: Technological choices for MemeGoat.
+---
+
+## Frontend
+- **Framework**: Next.js 15
+- **Style**: Tailwind CSS
+- **UI Library**: Lucide React, Radix UI
+
+## Backend
+- **Language**: Node.js (TypeScript) / NestJS or Go
+- **Database**: PostgreSQL
+- **Image Storage**: S3 or similar (Cloudinary, Uploadcare)
+
+## Documentation
+- **Framework**: Fumadocs