Update README, fix hardware detection, and optimize user management

[Cylae]

• Hardware Detection: Added sys.refresh_disks() to HardwareInfo::detect in server_manager/src/core/hardware.rs to ensure disk usage statistics are properly updated, matching the project's intent and improving dashboard accuracy.
• Web Interface Optimization: Replaced blocking tokio::task::block_in_place calls with tokio::task::spawn_blocking in add_user_handler and delete_user_handler within server_manager/src/interface/web.rs. This prevents blocking the async runtime during heavy operations like password hashing and file I/O, using a copy-on-write strategy for thread safety.
• README Update: Updated README.md (English and French sections) to include port 21027 (UDP) for the Syncthing service, reflecting the actual configuration.

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PR created automatically by Jules for task 15798482203852844863 started by @Cylae

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