feat: personal room name overrides (MSC4431-style)

Users can right-click any room and 'Rename for me...' to set a local
display name visible only to them. Stored in account data under
io.lotus.room_names. Shows a pencil indicator on renamed rooms.
useLocalRoomName() hook overrides useRoomName() when a local name exists.

Also includes:
- Rich room topic rendering via RoomTopicContent object (formatted_body
  support in RoomTopicViewer with HTML sanitization via sanitizeCustomHtml)
- Edit history viewer: clicking '(edited)' on a message opens a modal
  showing all prior versions with timestamps (EditHistoryModal.tsx)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/features/room/RoomViewHeader.tsx

@@ -544,7 +544,7 @@ export function RoomViewHeader({ callView }: { callView?: boolean }) {
                       priority="300"
                       truncate
                     >
-                      {topic}
+                      {topic.topic}
                     </Text>
                   </>
                 )}