[Core] Add FlashTransfer Logic, Fix Aot and mac sending image issue

[Lilyltt]

No description provided.

[Copilot]

Pull Request Overview

This PR implements FlashTransfer logic for image uploads as an alternative to Highway uploads, specifically targeting AOT (Ahead-of-Time) compilation scenarios and macOS environments where dynamic code compilation issues occur.

• Adds conditional upload logic to use FlashTransfer instead of Highway uploads on AOT and macOS platforms
• Implements a complete FlashTransfer upload system with chunked file transfers and SHA1 verification
• Adds new service packet classes for FlashTransfer protocol communication

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
Lagrange.Core/Message/Entities/ImageEntity.cs	Modified preprocessing to conditionally use FlashTransfer based on runtime platform detection
Lagrange.Core/Internal/Packets/Service/FlashTransferUploadResp.cs	Added response packet structure for FlashTransfer uploads
Lagrange.Core/Internal/Packets/Service/FlashTransferUploadReq.cs	Added request packet structures with chunked upload body and SHA1 state management
Lagrange.Core/Internal/Context/FlashTransferContext.cs	Implemented core FlashTransfer upload logic with chunked file processing
Lagrange.Core/BotContext.cs	Added FlashTransferContext initialization to bot context

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}