Fix #1851: Sort open groupchats alphabetically when grouped by domain

[cj-l920]

Problem Summary

Fixes #1851: Open Groupchats not sorted in any order

When the muc_grouped_by_domain configuration option is enabled, rooms within each domain group were not being sorted alphabetically. This made it difficult for users to find specific groupchats in the list.

Solution Approach

Added alphabetical sorting to the tplRoomDomainGroupList function in src/plugins/roomslist/templates/roomslist.js.

The fix ensures that:

1. Rooms are sorted by their display name (case-insensitive) before being grouped by domain
2. The existing domain sorting behavior is maintained
3. The sort is stable and consistent

Changes Made

• Modified tplRoomDomainGroupList() to sort rooms alphabetically using getDisplayName()
• Used case-insensitive comparison (toLowerCase()) for consistent ordering
• Added a copy of the rooms array to avoid mutating the original

Test Evidence

• Code compiles without errors
• Sorting logic follows the same pattern used in getRoomsToShow() in view.js
• Case-insensitive sorting ensures "Room A" and "room a" are ordered correctly
• Original array is not mutated (uses spread operator copy)

Example

Before (random order within domain):
example.com
Zebra Chat
Alpha Room
Beta Group
After (alphabetically sorted):
example.com
Alpha Room
Beta Group
Zebra Chat
Fixes #1851