🎨 Palette: Add Disabled State to Generate Button

[google-labs-jules]

💡 What: Added a disabled state to the "Generate Poster" button. It is now disabled after being clicked and is re-enabled once the poster generation is complete.

🎯 Why: Previously, the "Generate Poster" button remained active after being clicked, providing no feedback that an action was in progress. This could lead to users clicking the button multiple times, sending unnecessary requests and potentially causing errors. This change improves the user experience by providing clear visual feedback and preventing duplicate actions.

📸 Before/After:

Before: The button remained active while the poster was generating.
After: The button is now disabled, providing a clear visual cue that an action is in progress.

♿ Accessibility: Disabling the button during a loading state is an accessibility best practice. It prevents keyboard and screen reader users from inadvertently triggering the same action multiple times. The disabled attribute is programmatically understood by assistive technologies.

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PR created automatically by Jules for task 11711347028025239562 started by @anaxifty

[google-labs-jules]

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