🔐 feat: Use SecretInput for Sensitive Fields (#12955)

* feat: use SecretInput for sensitive fields

* fix: align auth SecretInput styles

* chore: remove unused password i18n keys

* fix: align SecretInput controls

* fix: use SecretInput for dynamic credentials

* fix: reveal SecretInput controls on hover

* fix: align SecretInput eye icon and modernize controls

The wrapper was a flex container, so passing 'mb-2' on the input made it
contribute its margin to the wrapper's cross-axis size — the controls overlay
spanned the inflated height and centered the toggle 4px below the input's
true center. Switching the wrapper to a plain relative block collapses height
back to the input.

Also tightens the toggle/copy buttons (size-7 rounded-md with hover:bg-surface-hover)
and adds a focus ring on the input. Auth pages still override className/buttonClassName
so login/register styling is unchanged.

* fix: remove focus ring from SecretInput

* fix: keep green focus border on auth secret inputs

SecretInput's modernized default uses focus-visible:border-border-heavy and
hover:border-border-medium, which Tailwind emits after the auth pages' focus:
rules and overrides them. Auth pages now also declare focus-visible:border-green-500
and hover:border-border-light so cn()/twMerge resolves them as the winners
when classes are concatenated.

* feat: add optional sensitive flag to MCP customUserVars

Dynamic MCP credential fields all rendered as masked SecretInputs, which
also hid non-secret setup values like usernames, project keys, and URLs.

Add an optional `sensitive` flag to customUserVars and the plugin auth
config. It defaults to masked when omitted, so existing configs keep the
safe-by-default behavior; set `sensitive: false` to render a field as
plain text. The flag is display-only — values remain encrypted at rest.

api/server/controllers/mcp.js

@@ -146,6 +146,7 @@ const getMCPTools = async (req, res) => {
               authField: key,
               label: value.title || key,
               description: value.description || '',
+              sensitive: value.sensitive,
             }));
             server.authenticated = false;
           }