fix(docker): install uv system-wide so runtime works under non-root

[clsferguson]

Install uv to /usr/local/bin in both builder and runtime stages (via UV_INSTALL_DIR=/usr/local/bin, UV_NO_MODIFY_PATH=1) so the final image’s USER app can execute uv without relying on /root/.local/bin. This removes the permission/path mismatch that caused “exec: 'uv': not found” at startup, while preserving BuildKit cache mounts for fast uv build/uv sync. The image still installs the graphiti-core wheel first, sets PATH to include /app/.venv/bin, and runs uv run uvicorn on port 8000 for a clean, reproducible launch in Compose/Portainer.

Summary

Install uv system-wide in both stages and keep a non-root runtime so uv is resolvable at container start, eliminating the /root traversal issue while retaining BuildKit caching and the existing multi-stage layout.

Type of Change

• Bug fix
• New feature
• Performance improvement
• Documentation/Tests

Objective

Make the runtime image consistent with a non-root user by placing uv in a world-accessible system path, ensuring the final CMD [uv run uvicorn ...] succeeds without altering runtime user or app startup behavior.

Testing

• Unit tests added/updated
• Integration tests added/updated
• All existing tests pass

Manual verification steps:

1. Build: DOCKER_BUILDKIT=1 docker build -t graphiti:latest .
2. Validate uv under non-root:
   docker run --rm graphiti:latest sh -lc 'id; command -v uv; uv --version'
3. Smoke test app:
   docker run --rm -p 8001:8000 graphiti:latest and curl http://localhost:8001/healthcheck
4. Deploy via Portainer stack and confirm container is running and healthy.

Breaking Changes

• This PR contains breaking changes

If this is a breaking change, describe:

• What functionality is affected
• Migration path for existing users

Checklist

• Code follows project style guidelines (make lint passes)
• Self-review completed
• Documentation updated where necessary (Dockerfile comments/README snippet)
• No secrets or sensitive information committed

Related Issues

Closes #[issue number]

[danielchalef]

All contributors have signed the CLA ✍️ ✅
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[clsferguson]

I have read the CLA Document and I hereby sign the CLA