Two issues:
1. Verlauf-Export CSV put the opaque file_code in the Link column when
the upload had no real URL, so the column looked like just a bunch
of IDs. Now only real http(s) URLs land in that column.
2. Hoster passwords and API keys were stored as plaintext in
electron-config.json. Now wrapped with Electron's safeStorage (DPAPI
on Windows, Keychain on macOS, libsecret on Linux) and stored as
'enc:v1:<base64>'.
Credentials are decrypted on load so in-memory flows stay unchanged,
and backups still export plaintext inside the existing .mhu envelope
so they remain portable between machines/users. Legacy plaintext
configs auto-migrate on next write.
