feat(frontend): public channels, self-excluded member picker, editable display name

- create-channel modal: Public checkbox (default off), self excluded from
  member list (creator auto-added), shows member display names
- Settings modal to edit your own display name
- members panel shows names and marks (you)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/auth-storage.ts

@@ -7,6 +7,7 @@ export type AuthSession = {
   user: {
     id: string
     email: string
+    name: string
   }
   guilds: Array<{
     nodeId: string