In Docker builds, .git directory is not available in the container,
so git describe --tags fails and fallback is '0.0.0'. Now:
- build.sh passes --build-arg APP_VERSION=${tag} to frontend build
- Dockerfile accepts ARG APP_VERSION and sets ENV
- vite.config.js checks process.env.APP_VERSION first, then git describe
svelte-markdown@0.4.1 declares peer dependency svelte@^4.0.0, but the
project uses svelte@^5.43.8. In clean Docker builds, npm ci strictly
validates peer deps and fails. Adding --legacy-peer-deps works around
the incompatibility until svelte-markdown supports Svelte 5.
