⚡ Bolt: Parallelize space service sync fetching

[kevinaboos]

💡 What: Use futures_util::future::join_all to concurrent-fetch avatar information instead of iterating via standard sequential await.
🎯 Why: Iterating over space rooms and asynchronously fetching avatar for each space using await sequentially causes blocking for I/O bounds when joining multiple spaces, potentially leading to performance bottlenecks during initial startup and synchronization. Parallelizing preserves order while drastically reducing blocking.
📊 Impact: Initial space info fetching sync time decreased considerably compared to sequential await logic.
🔬 Measurement: Verify startup initial rendering performance as well as checking space_service_loop logs.

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PR created automatically by Jules for task 10945762983898259262 started by @kevinaboos

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