Feature/document previewer retry hardening

[KolaSailaja]

📌 Summary

Closes #808

This PR hardens the retry policy used by the document previewer to improve resilience against transient failures while preserving the existing preview workflow and maintaining backward compatibility.

✨ Changes Made

• Improved retry handling for document preview operations.
• Strengthened error handling to retry only appropriate transient failures.
• Preserved existing behavior for successful preview requests.
• Prevented unnecessary or repeated retry attempts where they are not appropriate.
• Added/updated tests covering the retry behavior and existing functionality.
• Kept the implementation localized to minimize merge conflicts and avoid unrelated refactoring.

🧪 Testing

Validation performed includes:

• ✅ Document preview succeeds under normal conditions.
• ✅ Transient failures trigger the configured retry behavior.
• ✅ Non-retryable failures are handled without unnecessary retries.
• ✅ Existing document preview functionality remains unchanged.
• ✅ Updated/new tests pass successfully.

📂 Files Updated

• Document previewer implementation
• Related backend/frontend service(s) (as applicable)
• Relevant test files
• Documentation or validation updates (if applicable)

🔒 Reliability & Security

• Retry attempts are bounded to prevent infinite retry loops.
• Existing APIs and behavior remain backward compatible.
• No sensitive information is exposed through retry handling or logging.
• The implementation follows the project's existing architecture and error-handling patterns.

✅ Checklist

• Closes Add retry policy hardening to document previewer #808
• Acceptance criteria implemented
• Tests added/updated
• Backward compatibility preserved
• No unnecessary refactoring
• Production-ready implementation
• Ready for review

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