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>

compose.override.yml

@@ -0,0 +1,8 @@
+services:
+  if-curator:
+    build: .
+    network_mode: host
+    volumes:
+      - /code/if-curator/models:/models
+      - /code/if-curator/embeddings:/app/.if_cache
+      - /code/if-curator/output:/app/output