Blueprints Gallery LibraryL Add preview links to public blueprints

[katinthehatsite]

Related issues

Fixes STU-1710

How AI was used in this PR

Not needed, simple fix

Proposed Changes

This PR ensures that public blueprints have Live Preview link and allows to see the blueprint preview in the playground:

Testing Instructions

• Pull the changes from this branch
• Start Studio with npm start
• Enable the Blueprints Gallery feature flag in the top bar
• Click on Add site > Build a new site
• Scroll to the blueprints section
• Confirm that you can see the Live Preview links
• Confirm that the links open the preview with playground

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

[wpmobilebot]

📊 Performance Test Results

Comparing 19efc6a vs trunk

app-size

Metric	trunk	19efc6a	Diff	Change
App Size (Mac)	1408.66 MB	1408.66 MB	+0.00 MB	⚪ 0.0%

site-editor

Metric	trunk	19efc6a	Diff	Change
load	1494 ms	1500 ms	+6 ms	⚪ 0.0%

site-startup

Metric	trunk	19efc6a	Diff	Change
siteCreation	8089 ms	8081 ms	8 ms	⚪ 0.0%
siteStartup	4925 ms	4922 ms	3 ms	⚪ 0.0%

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Results are median values from multiple test runs.

Legend: 🟢 Improvement (faster) | 🔴 Regression (slower) | ⚪ No change (<50ms diff)