⚡ Bolt: Optimize production loop and population calculation

[google-labs-jules]

This PR implements two targeted performance improvements in the game's core logic:

1. Production Loop Optimization: In TurnEngine.ts, determining if a queued item was a building or a unit previously involved calling Object.values() on every iteration of the settlement production loop. This has been replaced with module-level Set constants, providing $O(1)$ lookup time and reducing garbage collection pressure.
2. Population Calculation Optimization: The calculatePopulation function in Settlement.ts was using a .filter().length pattern, which creates a new array every time it is called. This has been refactored into a simple for...of loop with a counter, avoiding unnecessary memory allocation.

These changes combined reduce CPU cycles and memory churn during the end-turn phase and when updating settlement UI.

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PR created automatically by Jules for task 8799583549388148644 started by @b0x1

[google-labs-jules]

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