* refactor: remove Nextra shims, migrate pages/ to app router, upgrade ESLint to v9
- Remove all nextra-shims and legacy pages/ directory
- Migrate subscribe, unsubscribe, and toolkit pages to app router
- Restructure config docs with guide-first setup steps and Tabs components
- Rewrite Docker install, OpenRouter, and custom endpoints docs
- Add Quick Start guide, Google Search docs, and image generation cross-links
- Update .gitignore
* feat: redesign toolkit and integrate into docs sidebar
Move credentials generator and YAML validator into the docs under
a new "Tools > Toolkit" sidebar section. Old /toolkit routes redirect
to /docs/toolkit.
Credentials generator: 2-column field grid, per-field copy buttons,
copy-all as .env block, empty state placeholder, design system tokens.
YAML validator: full-width theme-aware Ace Editor (chrome/twilight),
drag-and-drop overlay, result banners with icons, clear button,
no print margin.
Remove unused .error-marker and .custom-btn from style.css.
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Co-authored-by: Claude <noreply@anthropic.com>
