fix: separate account fetching from loop to avoid rate limiting

[0xzrf]

Summary

This PR refactors SurfnetRemoteClient::get_multiple_accounts() to batch RPC account fetches rather than issuing individual calls inside a loop. Instead of calling self.get_account_with_commitment() repeatedly per iteration, a single self.get_multiple_accounts_with_confirmation() call is made upfront and the results are processed afterwards.

What Changed

• Replaced repeated self.get_account_with_commitment() calls inside a loop with a single batched self.get_multiple_accounts_with_confirmation() call
• Reduced the number of RPC round-trips, lowering the risk of hitting rate limits under high load or large snapshot files

Context

This change was motivated by an existing comment inside SurfnetRemoteClient::get_multiple_accounts() that flagged the per-iteration RPC pattern as a potential rate-limiting concern. No new functionality is introduced — this is a pure refactor aimed at improving resilience when processing large snapshot files.

[MicaiahReid]

Great stuff, thank you @0xzrf!