[hot-fix] add timeout and retry logic to data fetch

[wackerow]

Description

• fix: enhance fetchEthStakedBeaconchain with timeout and retry logic
• feat: add/update api utils, constants and types
• feat: create dedicated beaconcha.in epoch and ethstore fetches—epoch contained validator count and total eth staked values (used on homepage, enterprise, staking pages), and ethstore contains APR data used on staking page
• feat: add/update mock data
• refactor: use new beacon chain api fetches with new timeout/retry/revalidation logic
• deprecate: fetchEthStakedBeaconchain
• ui: add fallback "—" for zero values on staking page

Prevents 500 response if API unavailable, using next revalidation to store cache from fetches, and guards against any fetching spikes or stampedes. Returns "error" state instead of throwing—subsequently displaying data error message for metric, instead of a 500 page.

Related Issue

• Fixes 500 Internal server error #16434

[netlify]

✅ Deploy Preview for ethereumorg ready!

Name	Link
🔨 Latest commit	6a4c844
🔍 Latest deploy log	https://app.netlify.com/projects/ethereumorg/deploys/68e2bc9806e77800087eccd8
😎 Deploy Preview	https://deploy-preview-16436--ethereumorg.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.
Lighthouse	7 paths audited Performance: 42 (🔴 down 1 from production) Accessibility: 94 (no change from production) Best Practices: 92 (no change from production) SEO: 100 (🟢 up 8 from production) PWA: 59 (no change from production) View the detailed breakdown and full score reports

---

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

[wackerow]

(User linking issues above has been reported for abuse to GitHub)