Added no-cache handling for preview requests

[9larsons]

no ref

Preview requests can include request-specific theme data, so these responses should not be stored or reused by frontend caches.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: e203568c-4039-48ff-b4c8-0b1911c2a899

📥 Commits

Reviewing files that changed from the base of the PR and between 9882356 and 82987b9.

📒 Files selected for processing (2)

• ghost/core/core/frontend/web/middleware/frontend-caching.js
• ghost/core/test/unit/frontend/web/middleware/frontend-caching.test.js

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Walkthrough

This pull request adds preview-mode caching behavior to the frontend caching middleware. The middleware now detects the x-ghost-preview request header and immediately returns noCache cache-control headers, bypassing all other caching logic. The change imports the preview service, implements the conditional check at the start of the middleware function, and includes a unit test validating the new behavior.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'Added no-cache handling for preview requests' accurately and clearly summarizes the main change: adding cache-control logic to prevent caching of preview requests.
Description check	✅ Passed	The description explains the rationale for the change—that preview requests contain request-specific theme data and should not be cached—which directly relates to the changeset.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch no-cache-preview

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