🎨 Palette: Add disabled and focus-visible states for better accessibility

[mapleleaflatte03]

💡 What: Added global CSS rules for :disabled and :focus-visible pseudo-classes to interactive elements (buttons, inputs, .cta, etc).

🎯 Why: The previous CSS lacked a visual indicator for disabled buttons (leading to poor user feedback on state) and didn't define a custom :focus-visible ring for keyboard navigation, making the application less accessible.

📸 Before/After: See attached verification media (disabled .operator-action buttons now have 0.5 opacity and not-allowed cursor, interactive elements have a 2px offset accent ring when focused via keyboard).

♿ Accessibility: Significantly improves WCAG compliance for focus indicators and clarity of disabled controls.

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PR created automatically by Jules for task 4119698659787012834 started by @mapleleaflatte03

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