⚡ Bolt: Optimize recent issues cache serialization

[google-labs-jules]

💡 What:
Optimized the /api/issues/recent endpoint by caching the serialized JSON string directly instead of the list of Pydantic models (or dicts).
Modified backend/main.py to store the result of json.dumps(data) in the cache.
On cache hits, it returns a Response object with media_type="application/json" and the pre-serialized content, bypassing FastAPI's JSONResponse serialization overhead.

🎯 Why:
The JSONResponse class performs serialization on every request, even if the data comes from the cache. By caching the final JSON string, we save the CPU cost of serializing the list of issues (which can contain complex nested structures like action_plan) on every read. This reduces latency for a frequently accessed endpoint.

📊 Impact:

• Reduces CPU usage for cached requests.
• Decreases latency for /api/issues/recent by skipping the serialization step (approx O(N) where N is response size).

🔬 Measurement:

• Added tests/test_recent_issues.py to verify caching behavior and format handling.
• Verified that the endpoint returns correct JSON and content-type.
• Verified robustness against legacy cache formats (list of dicts) to prevent errors during deployment/rollout.

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PR created automatically by Jules for task 15357320750871769866 started by @RohanExploit

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PR Details:

• Title: ⚡ Bolt: Optimize recent issues cache serialization
• Number: ⚡ Bolt: Optimize recent issues cache serialization #152

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• Code follows the project's style guidelines
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• Documentation updated (if applicable)
• No new warnings generated
• Tests added/updated (if applicable)
• All tests passing locally
• No breaking changes to existing functionality

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