✨ Feature (chat-input.tsx): Perplexity-like chat input box, extremely feature-rich

[KemingHe]

• auto-resize textarea
• keyboard shortcuts (enter and shift+enter)
• mode selection (auto, web-research, deep reasoning, etc.)
• model selection (different categories and providers)
• file attachement
• clickable submit/cancel button
• parent box auto grow and center the textarea when history is emptry
• don't for get to add documentation

[KemingHe]

mock comp (style only) for now, will come back for functionality