🎨 Palette: Add disabled state styles to buttons

[mapleleaflatte03]

💡 What: Added global CSS rules to apply reduced opacity (0.5) and a "not-allowed" cursor to all disabled buttons, .operator-action elements, and .cta elements.
🎯 Why: Previously, disabled buttons lacked visual feedback to indicate they were unclickable, making the UI less intuitive. This change ensures users immediately recognize disabled actions.
📸 Before/After: Visual tests were successfully performed using Playwright screenshots during development.
♿ Accessibility: Improved visual cues for users, making disabled state immediately recognizable globally across the platform.

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PR created automatically by Jules for task 5173308016032688732 started by @mapleleaflatte03

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