refactor: rename project to winnow

- Rename Python package directory if_curator/ → winnow/
- Update all imports, entry points, and CLI references
- Update pyproject.toml: name, scripts, package list, repository URL
- Update Dockerfile, compose.yml, entrypoint.sh, scheduler.py
- Update GitHub Actions workflow image names
- Update README

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Dockerfile

@@ -33,7 +33,7 @@ COPY pyproject.toml uv.lock ./
 RUN uv sync --frozen --no-dev \
     && uv cache clean
 
-COPY if_curator/ if_curator/
+COPY winnow/ winnow/
 COPY entrypoint.sh scheduler.py ./
 RUN chmod +x /app/entrypoint.sh