⚡ Bolt: [performance improvement] Optimize space sync N+1 requests

[kevinaboos]

💡 What: Extracted avatar fetching logic in space_service_sync.rs into get_joined_space_info and applied futures_util::future::join_all to execute asynchronous requests concurrently.
🎯 Why: Awaiting each avatar fetch inside a sequential for loop caused an N+1 query performance bottleneck during space list synchronization (initial sync, append, and reset), unnecessarily blocking list updates.
📊 Impact: Reduces total loading time for space syncing by executing all space data requests concurrently. Resolves the N+1 problem.
🔬 Measurement: Verify by joining multiple spaces or starting the app with multiple top-level spaces. The loading time should improve and logging should show concurrent requests. Also added a .jules/bolt.md entry.

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PR created automatically by Jules for task 6934061112531014119 started by @kevinaboos

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