Raylux 0.31.1: credentials leave the configuration file

Six credential fields no longer sit in clear text in the gateway's configuration.

Credentials move to a protected store

Mail passwords, messaging tokens, single-sign-on secrets, database passwords and device passwords now live in a separate, owner-only file, with the configuration holding only a reference.

• Migration runs on first start, keeps a backup of the previous configuration, and stores every credential before rewriting the configuration, so an interruption cannot lose one. A plain value left by hand-editing stays legal permanently.
• Rotating a password later never puts it back in the configuration.
• Reading a credential back returns a mask, never the value.
• If a credential cannot be found — a configuration restored onto a different gateway — the gateway names the affected features at start-up and keeps running rather than refusing to start.

Fixes that matter to users

• Test writes from the designer were broken for every control authored with a binding — buttons, toggles, sliders and text inputs. Nothing was written and nothing was logged.
• A bound text input in the running HMI wrote to the wrong tag, treating its own contents as the tag path.
• Every alarm-notification channel is now configurable without restarting the gateway. Mail had no configuration page at all; it has one now.

Upgrade notes

• The credential store is deliberately outside the backup. Restoring a backup onto a different gateway brings the references but not the secrets; the gateway names what needs re-entering. Restoring onto the same gateway resolves normally.