Use Netlify's auto-provided SITE_ID instead of custom env var

[pettinarip]

Summary

• Replace NETLIFY_BLOBS_SITE_ID with SITE_ID which is automatically provided by Netlify during builds
• Update docs to reflect the change
• Reduces required configuration since one less env var needs to be manually set

Test plan

• Verify Netlify build passes with only NETLIFY_BLOBS_TOKEN configured
• Verify data layer functions correctly fetch from Netlify Blobs

🤖 Generated with Claude Code

[netlify]

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Lighthouse	7 paths audited Performance: 61 (🟢 up 9 from production) Accessibility: 94 (no change from production) Best Practices: 100 (🟢 up 2 from production) SEO: 100 (no change from production) PWA: 59 (no change from production) View the detailed breakdown and full score reports

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