Reorganize layouts with dedicated admin sidebar (dark theme)

- Create admin layout with dark sidebar (zinc-900 background, light text)
- Move dashboard components to layout/dashboard/ subfolder
- Move admin components to layout/admin/ subfolder
- Admin sidebar has: Dashboard, Organizations, Users nav items
- Admin header shows "Admin" badge and "Exit Admin" link
- Update all route imports to use new barrel exports
- Add macOS sed syntax reference to CLAUDE.md

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -6,3 +6,11 @@ Before starting the dev server, check if it's already running:
 - Use `lsof -i :6827` or check for existing background tasks
 - The dev server runs on port 6827 (may fall back to 6828 if port is in use)
 - Start with `bun run --cwd apps/publisher-dashboard dev` or `devenv up`
+
+## macOS sed Syntax
+
+macOS uses BSD sed which differs from GNU sed:
+- In-place edit requires empty string for backup: `sed -i '' 's/old/new/g' file`
+- GNU sed (Linux): `sed -i 's/old/new/g' file`
+- Use `|` as delimiter when patterns contain `/`: `sed -i '' 's|old/path|new/path|g' file`
+- For multiple files: `for f in *.txt; do sed -i '' 's/old/new/g' "$f"; done`