feat: Toast: card effect

[joduplessis]

• Toast stack effect — toasts now render as a layered card stack (opacity + scale gradient for depth, clamped to 3 visible layers) with a new paused prop and suffix slot on ToastMessage. Progress bar switched from JS-driven setTimeout + width transition to pure CSS animation, fixing restart/pause behaviour.
• Color token refresh — accent hue shifted (245 → 280) across the color.json ramp; knock-on CSS updates landed across ~85 component stylesheets to keep contrast and hover states correct.
• Color-relative button hovers — button.css rewritten to derive hover/active from the base color rather than hardcoded values, making variants consistent without per-variant overrides.
• Context rename — fold.context.tsx → app.context.tsx (re-exported from contexts/index.ts).
• Tighter stack distance — reduced default spacing between stacked toasts.

[netlify]

✅ Deploy Preview for fold-storybook ready!

Name	Link
🔨 Latest commit	cfc087e
🔍 Latest deploy log	https://app.netlify.com/projects/fold-storybook/deploys/69e4ee51154a8a00080f9f06
😎 Deploy Preview	https://deploy-preview-348--fold-storybook.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.