feat(chat): implement XEP-0461 threaded reply UI

[AmoghParmar]

Description

This PR adds full reply-to support in the Jitsi Meet chat panel.

It captures replyToId from both MESSAGE_RECEIVED and PRIVATE_MESSAGE_RECEIVED, passes it through _onConferenceMessageReceived() and _handleReceivedMessage(), stores it as replyToMessageId in the reducer, and extends IMessage with the same field.

It also adds reply state handling in the UI:

• SET_REPLY_MESSAGE action and setReplyMessage() action creator.
• Reply preview banner above ChatInput with a dismiss button.
• Inline reply preview inside ChatMessage.
• Reply option in the message menu.

Finally, replyToMessageId is passed through sendMessage() and sendTextMessage() so XEP-0461 reply stanzas are sent over XMPP.

Related Issue

#17196

Motivation and Context

This change adds the UI and state-management side of XEP-0461 threaded replies. The XMPP stanza construction fix is handled in lib-jitsi-meet.

How Has This Been Tested?

Manually tested the chat reply flow in Jitsi Meet. Verified that reply state appears in the input, reply previews render correctly, and reply messages are sent with the expected metadata.

Screenshots or GIF (In case of UI changes):

Before:

• No threaded reply UI in chat.

After:

• Reply preview shown in chat input and message flow.

Related PRs

• lib-jitsi-meet fix: fix(chat): fix XEP-0461 reply stanza construction in sendMessage lib-jitsi-meet#3024

[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 :(.