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>

.github/workflows/docker-publish.yml

@@ -12,7 +12,7 @@ on:
 
 env:
   REGISTRY: ghcr.io
-  IMAGE_NAME: sudolulo/if-curator-headless
+  IMAGE_NAME: sudolulo/winnow
 
 jobs:
   verify-lockfile:

.github/workflows/release.yml

@@ -136,6 +136,6 @@ jobs:
           cache-from: type=gha
           cache-to: type=gha,mode=max
           tags: |
-            ghcr.io/sudolulo/if-curator-headless:latest
-            ghcr.io/sudolulo/if-curator-headless:${{ steps.tag.outputs.TAG }}
+            ghcr.io/sudolulo/winnow:latest
+            ghcr.io/sudolulo/winnow:${{ steps.tag.outputs.TAG }}