Improve password management in transfer create

[HanXHX]

• Add password confirmation (when prompted)
• Add flag to autogenerate passphrase (and displayed in console)

[Copilot]

Pull request overview

This PR improves retyc transfer create passphrase handling by adding interactive confirmation when the user is prompted, and by introducing an option to auto-generate a secure random passphrase and display it after the transfer is created.

Changes:

• Added --generate-passphrase flag to generate a secure random transfer passphrase and print it after completion.
• Added passphrase confirmation when prompting interactively.
• Updated README command description to document the new flag.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
cmd/transfer.go	Adds passphrase generation + printing, interactive confirmation, and a mutually-exclusive flag pairing with --passphrase.
README.md	Documents the new --generate-passphrase option on the transfer create command.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.