unified streaming and non-streaming

...reate-llama/templates/simple/nextjs/app/api/chat/route.ts

...lama/templates/simple/nextjs/app/components/chat-item.tsx

...a/templates/simple/nextjs/app/components/chat-section.tsx

...a/templates/simple/nextjs/app/components/message-form.tsx

...templates/simple/nextjs/app/components/ui/chat-avatar.tsx

.../templates/simple/nextjs/app/components/ui/chat-input.tsx

...a/templates/simple/nextjs/app/components/ui/chat-item.tsx

...mplates/simple/nextjs/app/components/ui/chat-messages.tsx

...mplates/simple/nextjs/app/services/chatStorage.service.ts

packages/create-llama/templates/simple/nextjs/package.json

...emplates/streaming/nextjs/app/components/chat-section.tsx

...plates/streaming/nextjs/app/components/ui/chat-avatar.tsx

...mplates/streaming/nextjs/app/components/ui/chat-input.tsx

...emplates/streaming/nextjs/app/components/ui/chat-item.tsx

...ates/streaming/nextjs/app/components/ui/chat-messages.tsx