make backend routing work

[Gawor270]

No description provided.

[Copilot]

Pull Request Overview

This PR configures the backend to properly handle routing in a containerized environment by binding the Fastify server to all network interfaces and updating the frontend's backend URL configuration to use relative paths.

• Configures Fastify to listen on all network interfaces (0.0.0.0) for Docker networking
• Updates backend URL configuration from absolute nginx proxy path to relative API path

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
deep-sea-stories/packages/backend/src/main.ts	Adds host binding to enable external access to the backend service in Docker
deep-sea-stories/docker-compose.yml	Changes backend URL from nginx proxy path to relative API endpoint

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