⚡ Bolt: Offload synchronous SQLite persistence calls to avoid blocking event loop

[Adityasingh-8858]

💡 What
Wrapped all direct SQLite persistence calls (create_transfer_record, set_agent_b, list_transfers, get_transfer) in backend/main.py using await asyncio.to_thread(). Added an entry to Bolt's journal (.jules/bolt.md) explaining the rationale.

🎯 Why
Executing standard Python synchronous SQLite operations inside FastAPI async def endpoints blocks the entire asyncio event loop for the duration of the disk I/O. By offloading these operations to a thread pool with asyncio.to_thread, the main event loop remains free to handle concurrent incoming requests, significantly improving the backend's concurrency and responsiveness.

📊 Impact
Prevents event loop starvation during database reads/writes. In high-concurrency situations, this allows the server to process concurrent API requests rather than blocking all connections while waiting for a single synchronous disk write to complete.

🔬 Measurement
Run the server under load or use a script (e.g. test_persistence_sync.py) to verify that async tasks (like a heartbeat printer) continue firing seamlessly while database writes are occurring, confirming the event loop is no longer blocked. Verified all automated pytest suites passed flawlessly.

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PR created automatically by Jules for task 8555564245407436068 started by @Deepaksingh7238

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[Copilot]

Pull request overview

This PR improves FastAPI backend responsiveness by moving synchronous SQLite persistence operations off the asyncio event loop and into a thread pool, preventing event-loop blocking during DB reads/writes.

Changes:

• Offloaded SQLite writes (create_transfer_record, set_agent_b) to await asyncio.to_thread(...) in async endpoints.
• Offloaded SQLite reads (list_transfers, get_transfer) to await asyncio.to_thread(...) to avoid blocking under concurrent load.
• Added a Bolt journal entry documenting the rationale and the recommended pattern going forward.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
backend/main.py	Wrapes synchronous persistence calls in asyncio.to_thread within async FastAPI endpoints to avoid blocking the event loop.
.jules/bolt.md	Documents the learning and standard action (“always offload sync SQLite calls”) for future changes.

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