feat: publish to ClawHub as last30days-official

- Add ClawHub badge and install command to README
- Update SKILL.md: metadata.openclaw canonical key, license/author/repository fields, optionalEnv vars, added instagram/polymarket tags
- Add .clawhubignore to exclude binary assets and dev files from bundle

Published: https://clawhub.ai/skills/last30days-official

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

.clawhubignore

@@ -0,0 +1,19 @@
+# Exclude binary assets and dev/test artifacts from ClawHub bundle
+assets/
+docs/
+fixtures/
+tests/
+plans/
+agents/
+variants/
+release-notes.md
+SPEC.md
+TASKS.md
+SKILL-original.md
+*.jsonl
+*.json
+*.mp3
+*.jpeg
+*.jpg
+*.png
+*.gif