Build and push Docker image to GitHub Container Registry

[Nonetss]

Summary

Adds a GitHub Actions workflow that builds the app image and pushes it to GitHub Container Registry (GHCR) on every push to master. Deployments can use docker compose with a prebuilt image, so you don’t need to clone the full repository or build the image on the server.

Changes

• Workflow (.github/workflows/docker-build.yml): checkout, log in to ghcr.io with GITHUB_TOKEN, tag with docker/metadata-action, build and push with docker/build-push-action.
• Tags: latest on the default branch, branch tags, and short SHA tags with a branch prefix.
  docker-compose.prod.yml: the api service uses ghcr.io/vkfolio/orio-search:latest (alongside SearXNG, Redis, and optional Ollama via the llm profile).