⚡ Bolt: Remove LINQ ToDictionary allocations on hot paths

[google-labs-jules]

💡 What: Replaced numerous high-overhead LINQ allocations (.ToDictionary(), .GroupBy(), .Where(), etc.) with manual looping and pre-sized dictionaries in NetworkSimulationEngine.cs, TemporalNetworkSimulationEngine.cs, and MixedRouting.cs.

🎯 Why: In high-frequency hot paths like routing simulations, chaining LINQ .ToDictionary() forces the CLR to allocate delegates, closures, intermediate sequences, and dictionary wrappers. This generates massive garbage collection pressure. Pre-sizing and manually populating standard loops entirely eliminates this overhead.

📊 Impact: Reduces memory allocations during network simulation iterations and improves overall throughput.

🔬 Measurement: Verified functionality is identical by successfully running the MedWNetworkSim test suite. Tests pass without regressions.

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PR created automatically by Jules for task 6166298327440255012 started by @wnj00524

[google-labs-jules]

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