fix(conference): suppress redundant reason dialog on host-terminated session

[iospro]

Problem

When a moderator ends the conference for all participants via "End meeting for all",
the server sends CONFERENCE_DESTROYED with reason "The meeting has been terminated".
This reason string gets passed to hangup() / notifyConferenceFailed() and shows up
as an error dialog to participants — even though it is not an error, but a normal
intentional termination by the host.

Solution

Check the destroy reason against TRIGGER_READY_TO_CLOSE_REASONS['dialog.sessTerminatedReason']
(the single source of truth already defined in constants.ts) and pass an empty
localizedReason in that case, suppressing the redundant error notification.

Changes

• middleware.web.ts — extract localizedReason, clear it for sessTerminatedReason
• middleware.native.ts — same fix for React Native path

Behaviour

Scenario	Before	After
Host ends meeting for all	Error dialog shown to participants	Clean disconnect, no dialog
Server crash / unexpected destroy	Error reason shown correctly	Unchanged

[jitsi-jenkins]

Hi, thanks for your contribution!
If you haven't already done so, could you please make sure you sign our CLA (https://jitsi.org/icla for individuals and https://jitsi.org/ccla for corporations)? We would unfortunately be unable to merge your patch unless we have that piece :(.