⚡ Bolt: batch save state updates for better performance

[georgi]

💡 What: Implement save_many method in Database Adapters (SQLite, PostgreSQL, Supabase) to handle bulk list of dicts. Update DBModel base class to add a save_many class method that exposes this interface to other classes. Update StateManager to use RunNodeState.save_many over iterating through instances calling state.save() for each one.
🎯 Why: StateManager handles bulk enqueued states from executing workflow nodes but processed them with single row updates. This causes high DB roundtrips and slows down node executions with large DAGs.
📊 Impact: Eliminates N+1 writes in StateManager._process_batch. Significant reduction in DB write time/latency, leading to lower node start/stop latencies.
🔬 Measurement: Can be observed with large graphs by tracking the duration of _process_batch.

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PR created automatically by Jules for task 12008955676744676120 started by @georgi

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