⚡ Optimize HistoryManager get_entry with a secondary dictionary index

[LebToki]

💡 What: Added a secondary index (_history_index dictionary) that maps entry IDs to their corresponding GenerationHistory objects. This dictionary is kept in sync during additions, deletions, clears, and history loading/saving operations.

🎯 Why: The previous get_entry method used a linear search loop over the list (O(n)), which caused unnecessary CPU usage and performance bottlenecks when there are many items in the history. Looking up an entry by ID is now a dictionary get operation, which resolves in O(1) time complexity.

📊 Measured Improvement:
I created a script (benchmark_history.py) to measure the baseline performance before optimizing and again after the implementation. The benchmark added 1000 items to the HistoryManager and looked up all 1000 items 100 times in a loop.

• Baseline: ~1.8802 seconds
• With Dictionary Index: ~0.0095 seconds
• Change: This change resulted in a ~197x speedup (a 99.5% reduction in lookup time) for get operations when dealing with large history sizes.

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PR created automatically by Jules for task 12576992903923854241 started by @LebToki

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