feat: new visual notch tiers, color, roles, digits

[bryanlundberg]

What does this PR do?

• Notch reduced to 3 tiers: double cut only on the primary button and record objects, one 12px cut on containers, square corners on fields, chips, rows and controls.
• Native corner-shape: bevel where supported, so keyboard focus is visible on notched controls.
• One item-card class replaces the solve, cube and algorithm card styles.
• Removed visual noise: ripple, logo glitch, rotating beams, modal textures, glows, side stripes, dotted backgrounds.

Screenshots or GIFs (if applicable)

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• I have reviewed my code and believe it is ready for merging.
• I understand that this PR may be subject to review and changes.
• I agree to abide by the code of conduct and contributing guidelines of this project.