Lohnt sich dein eigenes Dashlane?

Build me a personal password vault to replace Dashlane. Requirements:

- A Node CLI: `vault add <name>`, `vault get <name>`, `vault list`, `vault gen`.
  `get` copies the secret to the clipboard with clipboardy and clears it after
  20 seconds.
- The vault is one encrypted file at ~/.vault/store.age, encrypted with age
  (shell out to the age binary), key derived from a master passphrase prompted
  at runtime and never written to disk.
- Each entry: name, username, password, URL, notes, updated timestamp. JSON
  inside the encrypted file, decrypted only in memory.
- `vault gen` produces a 24-char random password via crypto.randomBytes, plus a
  4-word diceware option for passphrases.
- `vault backup` writes a datestamped encrypted copy to ~/.vault/backups/ so I
  can sync it with any file-sync tool I already trust.
- Fully local: no accounts, no telemetry, zero network calls.
- Out of scope: browser-extension autofill, passkeys, breach alerts, sharing.
  Do not invent any crypto, use age exactly as shipped.
- README: state plainly that KeePassXC or Bitwarden is the sane choice for most
  people, and that a forgotten master passphrase means the vault is gone.