Introduce a full ChatSettingsModal component for managing group chats (rename/icon upload, add/remove members, toggle moderators, leave/delete) and wire it into ChatRoomPage with a settings button. Add reply preview support end-to-end: new ReplyToSerializer and members_detail in backend serializers, updated frontend Message model (reply_to now contains preview object), and UI changes to Message to render reply excerpts. Improve socket handling to attach reply previews when available. Tweak backend Dockerfile to optionally install Windows/corporate CA bundle only if present and move pip install after copying source. Add Czech translations and small tooling/.claude config enhancements.
