⚡ Bolt: Prevent main thread blocking during I/O operations

[acebytes]

💡 What: Refactored synchronous file I/O and process execution within @MainActor async methods to run inside await Task.detached { ... }.value. Added a performance learning to .jules/bolt.md.
🎯 Why: In Swift Concurrency, async methods on a @MainActor execute on the main thread. If they perform synchronous, blocking operations (like fetching URLResourceValues for DiskInfo or waiting for a Process to exit), they will block the UI thread, causing freezes and degraded user experience.
📊 Impact: Eliminates UI stutter/freezes when initiating a scan (which checks disk info) and during the Docker prune operation (which executes a blocking sub-process). Application remains fully responsive.
🔬 Measurement:

1. Build and run the app.
2. Trigger a scan and observe the UI responsiveness.
3. Trigger a Docker prune via the menu and verify the UI does not hang while the prune process is running.

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PR created automatically by Jules for task 7742641724414580977 started by @acebytes

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