Modularize simulateur_bluebot.html JS into three separate scripts

[Animation-EdNum]

Extracted the massive inline JavaScript from simulateur_bluebot.html into three logically distinct vanilla JavaScript files located under assets/js/bluebot/:

1. bluebot-engine.js: Contains all the internal state definitions, execution engines, and pathfinding algorithms.
2. bluebot-skins.js: Houses configurations for environments, skins, and cosmetic variables logic.
3. bluebot-ui.js: Manages the DOM manipulation, layout generation, and user interactions.

All existing Playwright E2E tests pass reliably.

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PR created automatically by Jules for task 2640221035758161071 started by @Animation-EdNum

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