feat: add chat and file management APIs, implement chat loading and saving functionality

- Introduced new API endpoints for chat management including posting and retrieving chat messages.
- Implemented file upload and deletion functionalities for chat and other files.
- Added utility functions for streaming text and loading chat data.
- Created TypeScript types for models and agents used in the application.
- Configured TypeScript settings for server and project.
- Added favicon and workspace configuration for pnpm.

tsconfig.json

@@ -0,0 +1,4 @@
+{
+  // https://nuxt.com/docs/guide/concepts/typescript
+  "extends": "./.nuxt/tsconfig.json"
+}