feat: add fullscreen functionality to prompt input

The change

Description Add fullscreen toggle functionality to the prompt input component on mobile devices. fix #3244 Changes • Added fullscreen mode with expand/minimize button • Implemented mobile detection using useIsMobile hook • Auto-expand triggers when content exceeds 5 lines or 300 characters • auto-minimize after submit Demo <img width="429" height="916" alt="image" src="https://github.com/user-attachments/assets/1c562a73-3d0f-4b75-83cc-2cb56b90c198" /> <img width="427" height="916" alt="image" src="https://github.com/user-attachments/assets/3da0bd87-5009-452a-b14e-f5f2bbcb7c64" /> <img width="505" height="957" alt="image" src="https://github.com/user-attachments/assets/6e1e714a-d682-418c-a803-b6275f43e5a6" /> <img width="478" height="955" alt="image" src="https://github.com/user-attachments/assets/2a9a3174-a893-4b2f-af02-4b57f861107d" /> [Video Demo | GDrive](https://drive.google.com/file/d/1mqEJCsp-4BPzufrCku_wxdJk6mvjhrYx/view?usp=sharing) Testing • ✓ Tested on mobile viewport • ✓ Fullscreen toggle works via button click • ✓ Submitting in fullscreen mode auto-minimizes Checklist • ✓ Code follows project conventions • ✓ No breaking changes • ✓ Tested locally

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