feat(claude-code): add project settings and commands

- Add .claude/settings.json with permissions and hooks
- Add /format-lessons slash command
- Add .claude/settings.local.json to .gitignore

.claude/commands/format-lessons.md

@@ -0,0 +1,8 @@
+Format all lesson JSON files including localized versions.
+
+Run prettier on all lesson files:
+```bash
+npx prettier --write "lessons/**/*.json"
+```
+
+This formats both root lessons (`lessons/*.json`) and localized lessons (`lessons/ar/`, `lessons/de/`, `lessons/es/`, `lessons/pl/`, `lessons/uk/`).