feat: add file upload support to project evaluation page

[HuiNeng6]

Summary

This PR adds file upload support to the project evaluation page as requested in issue #95.

Changes

1. New File Model (\models/File.ts)

• Created \S3FileModel\ class extending \FileModel\ from \mobx-restful-table\
• Implements \upload\ method with signed URL support
• Implements \delete\ method for file removal

2. Updated Project Evaluation Page (\pages/dashboard/project/[id].tsx)

• Added file input button with multi-select support
• Added paste event listener to capture images from clipboard
• Added drag & drop support for file upload
• Added \uploadFilesAndSendMessages\ method to upload files and send as ConsultMessage

Features

• File Input Button: Users can click the attachment button to select multiple files
• Paste Support: Users can paste images directly from clipboard
• Drag & Drop Support: Users can drag and drop files into the chat area
• Supported File Types: Images, PDF, DOC, DOCX, TXT, MD

Usage

1. Click the 📎 button to select files
2. Or paste images directly (Ctrl+V)
3. Or drag and drop files into the chat area

Files will be uploaded and sent as messages with the format:
\
📎 filename
[file_url]
\\

Closes #95