Refactor documentation and remove unused Docker files

- Updated setup documentation to reference CONTRIBUTING.md instead of README.md.
- Removed .dockerignore and Dockerfile from the frontend directory as they are no longer needed.
- Updated Discord link in mkdocs.yml to the new invite link.
- Deleted project_structure.txt as it is no longer relevant.

Author: rahulharpal1603

CONTRIBUTING.md

@@ -8,14 +8,6 @@ Hi there! Thank you for considering contributing to **PictoPy** – we’re exci
 
 1. Setup Using Script (Recommended Approach): [Guide](docs/Script_Setup_Guide.md)
 2. Setup Manually: [Guide](docs/Manual_Setup_Guide.md)
-3. Docker Setup:
-
-   - Docker Compose Setup: [Guide](./docs/docker-compose/readme.md)
-   - Setup using Dockerfile
-
-     - For setting up the frontend, follow the instructions in the [Frontend Setup Guide](./docs/frontend/docker-setup.md).
-       </br>
-     - For setting up the backend, follow the instructions in the [Backend Setup Guide](./docs/backend/docker-setup.md).
 
 ## Docs Website Setup