Implement syntax: secret move/mv <vault>:<secret> <vault>[:<secret>]
- Copies all versions to destination vault with re-encryption
- Deletes source after successful copy (true move)
- Add --force flag to overwrite existing destination
- Support both within-vault rename and cross-vault move
- Add shell completion for vault:secret syntax
- Include integration tests for cross-vault move
- Vault creation now prompts for mnemonic if not in environment
- Automatically creates passphrase unlocker during vault creation
- Prevents 'missing public key' error when adding secrets to new vaults
- Updates tests to reflect new vault creation flow
