Add Classical and Rock Genres with Grouping Logic

[tailot]

This PR implements two new music genres: Classical and Rock.

Key Changes:

• Genre Definitions: Added classical (70 BPM, C Maj) and rock (110 BPM, E Min) to js/config.js.
• Grouping Mechanism: Modified js/beatGenerator.js to generate note patterns in groups of 2, 3, or 4 for these specific genres. Notes for melody and bass are synchronized to trigger only on these group starts.
• Dynamic Attenuation: Implemented a "velocità bassa" (low velocity) requirement by applying a 0.6x multiplier to the energy parameter for these genres, resulting in a softer sound.
• UI Integration: Added the new genres to the selection dropdown in index.html and updated the _getGenreFamily logic in js/uiController.js.
• Backward Compatibility: Ensured that existing genres (like techno, dnb, etc.) maintain their original rhythmic and dynamic behavior.

Verification:

• Automated tests via Playwright confirm that selecting the new genres updates the state (BPM, display) and triggers note generation.
• Visual inspection via screenshots confirms UI consistency.
• Regression testing confirms no impact on existing genres.

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PR created automatically by Jules for task 14591624696097442080 started by @tailot

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