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/components/ui/Avatar.tsx

@@ -58,8 +58,7 @@ function getDotMetrics(avatarSize: number, ringWidth: number = 0) {
 export function Avatar({ src, name, size = 40, status, className = '', onClick, user, userId, ring, avatarColor }: AvatarProps) {
   const openUserProfile = useUIStore((s) => s.openUserProfile);
   const initials = name.charAt(0).toUpperCase();
-  // Match prototype: 24px→10px, 32-34px→12px, 40px→15px, 56px+→18px
-  const fontPx = size <= 24 ? 10 : size <= 34 ? 12 : size <= 44 ? 15 : 18;
+  const fontPx = Math.round(size * 0.4);
   const gradient = getAvatarGradient(userId ?? user?.homeUserId ?? user?.id, name, avatarColor ?? user?.avatarColor);
 
   const ringWidth = ring?.width ?? 0;