Update skills: add website-creator, mql-developer, ecommerce-astro

Changes:
- Add FAL_KEY and GEMINI_API_KEY to .env.example
- Update picture-it to use ~/.config/opencode/.env (unified creds)
- Remove shodh-memory skill (no longer used)
- Remove alphaear-* skills (deprecated)
- Remove thai-frontend-dev skill (replaced by website-creator)
- Remove theme-factory skill
- Add mql-developer skill (MQL5 trading)
- Add ecommerce-astro skill (Astro e-commerce)
- Add website-creator skill (Next.js + Payload CMS)
- Update install script for new skills

skills/website-creator/design/references/slides-create.md

@@ -0,0 +1,4 @@
+Invoke `slides` skill to create persuasive HTML slides using design tokens, Chart.js, and the slide knowledge database.
+
+## Task
+<task>$ARGUMENTS</task>