feat: add player invitation and autojoin functionality

Implement a system to invite players via generated URLs that
automatically configure their name and role.

- Add `InviteDialog` to allow users to generate and copy invite links
- Implement autojoin logic in `ConnectDialog` based on URL parameters
- Add an "+ invite" button to the `JournalPanel` player list
- Ensure `autojoin` parameter is stripped on disconnect to allow
  manual connection later

src/components/stores/journalStream.ts

@@ -583,6 +583,9 @@ export function disconnectStream(): void {
   setState("connected", false);
   setState("connectionStatus", "disconnected");
   setState("players", {});
+
+  // Strip autojoin param so the dialog shows normally on next connect
+  removeUrlParam("autojoin");
 }
 
 // ---------------------------------------------------------------------------