Implement Backend Architecture and Server Setup

[Thor-Dahl]

Design and implement the backend infrastructure required to support user accounts, posts, boards, comments, and tag based filtering for HubPixel.

Scope:

1. Select backend stack and architecture
2. Set up server project structure
3. Implement database schema for users, posts, boards, tags, and messages
4. Implement authentication system
5. Create REST or API endpoints for core features
6. Connect frontend to backend API
7. Implement basic error handling and validation