feat: presence avatar border rings (P5-18) + room emoji prefix support (P5-6)

P5-18: PresenceRingAvatar wrapper component applies a 2px box-shadow
ring to user avatars — green (online), yellow (idle/unavailable), red
(DND via status_msg='dnd'), no ring (offline). Applied to: message
timeline sender avatars, members drawer (members + knock requests),
@mention autocomplete, and inbox notification senders.

P5-6: Leading emoji in room names renders at 1.15× in the sidebar via
Unicode emoji regex detection in RoomNavItem. Emoji picker (EmojiBoard
in PopOut) added to all three room-name inputs: Create Room dialog
(converted to controlled input), Room Settings name field (shown only
when canEditName), and the "Rename for me" local rename dialog.

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

src/app/pages/client/inbox/Notifications.tsx

@@ -96,6 +96,7 @@ import {
 } from '../../../hooks/useMemberPowerTag';
 import { useRoomCreatorsTag } from '../../../hooks/useRoomCreatorsTag';
 import { useRoomCreators } from '../../../hooks/useRoomCreators';
+import { PresenceRingAvatar } from '../../../components/presence';
 
 type RoomNotificationsGroup = {
   roomId: string;
@@ -478,25 +479,27 @@ function RoomNotificationsGroupComp({
               <ModernLayout
                 before={
                   <AvatarBase>
-                    <Avatar size="300">
-                      <UserAvatar
-                        userId={event.sender}
-                        src={
-                          senderAvatarMxc
-                            ? (mxcUrlToHttp(
-                                mx,
-                                senderAvatarMxc,
-                                useAuthentication,
-                                48,
-                                48,
-                                'crop',
-                              ) ?? undefined)
-                            : undefined
-                        }
-                        alt={displayName}
-                        renderFallback={() => <Icon size="200" src={Icons.User} filled />}
-                      />
-                    </Avatar>
+                    <PresenceRingAvatar userId={event.sender}>
+                      <Avatar size="300">
+                        <UserAvatar
+                          userId={event.sender}
+                          src={
+                            senderAvatarMxc
+                              ? (mxcUrlToHttp(
+                                  mx,
+                                  senderAvatarMxc,
+                                  useAuthentication,
+                                  48,
+                                  48,
+                                  'crop',
+                                ) ?? undefined)
+                              : undefined
+                          }
+                          alt={displayName}
+                          renderFallback={() => <Icon size="200" src={Icons.User} filled />}
+                        />
+                      </Avatar>
+                    </PresenceRingAvatar>
                   </AvatarBase>
                 }
               >