[FEATURE] Project Workspaces for Persistent Context Across Multiple Chats

## Description

Working on long-term projects often requires multiple conversations covering different aspects such as planning, implementation, debugging, documentation, and research. As the number of conversations grows, it becomes increasingly difficult to keep everything organized and maintain continuity.

Currently, every conversation exists independently. This requires users to frequently switch between multiple chats, search through chat history, or repeatedly provide the same project context when starting a new conversation. While DeepSeek supports long context within a single chat, managing large projects across multiple conversations becomes less efficient and introduces unnecessary friction.

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## Proposed Solution

Introduce a **Project Workspace** feature, similar to the **Projects** feature in ChatGPT, where users can group multiple related conversations under a single project.

A Project Workspace could provide:

- Multiple conversations within a single project.
- A project-based folder structure for better organization.
- Shared project context across conversations.
- Project-level file uploads that can be referenced by any conversation in the project.
- Project-specific instructions or preferences.
- Easy navigation between related conversations without losing continuity.

This would create a more organized workflow for long-term projects and significantly reduce the need to repeatedly provide the same context when switching between conversations.