feat: channel permissions UI, DM Sans font, private channel filtering, migration fix

- Rewrite ChannelSettingsModal with full tri-state permission override UI
  for roles and members (allow/neutral/deny per permission bit)
- Switch font from Inter to self-hosted DM Sans (woff2 variable fonts)
- Add client-side VIEW_CHANNEL filtering in ChannelSidebar for private channels
- Broadcast isPrivate flag on channel override changes
- Fix voice permission bit migration: gate behind persistent flag to prevent
  repeated re-runs that stripped STREAM from @everyone roles
- Add speakingUserIds set to voice store for efficient user-level lookups
- Clear current channel view when a channel is deleted
- Move .glass-strip to @layer utilities for proper CSS specificity
- Simplify avatar initials font size to proportional formula

packages/web/src/hooks/useWebSocket.ts

@@ -612,6 +612,11 @@ function handleEvent(origin: string, event: ServerEvent): void {
       if (event.spaceId === curSpaceId3) {
         setChannels3(curChannels3.filter(c => c.id !== event.channelId));
       }
+      // If the user is currently viewing the deleted channel, clear it
+      const { currentChannelId: deletedViewChannelId } = useChatStore.getState();
+      if (deletedViewChannelId === event.channelId) {
+        useChatStore.getState().setCurrentChannel(null);
+      }
       chPermsMap3.delete(event.channelId);
       ctsMap3.delete(event.channelId);
       coMap3.delete(event.channelId);