feat: Import 35+ skills, merge duplicates, add openclaw installer

Major updates:
- Added 35+ new skills from awesome-opencode-skills and antigravity repos
- Merged SEO skills into seo-master
- Merged architecture skills into architecture
- Merged security skills into security-auditor and security-coder
- Merged testing skills into testing-master and testing-patterns
- Merged pentesting skills into pentesting
- Renamed website-creator to thai-frontend-dev
- Replaced skill-creator with github version
- Removed Chutes references (use MiniMax API instead)
- Added install-openclaw-skills.sh for cross-platform installation
- Updated .env.example with MiniMax API credentials

skills/gif-sticker-maker/references/requirements.txt

@@ -0,0 +1,5 @@
+# Python dependencies
+requests>=2.28
+
+# System dependency (install separately):
+#   ffmpeg — brew install ffmpeg (macOS) / apt install ffmpeg (Ubuntu)