- New InviteFriendsModal component: fetches friends list, sends game
invite via notification socket with per-friend sent confirmation
- Multiplayer (GamePage): invite button below copy link, hidden after game ends
- Correspondence: invite button in waiting-for-opponent card
- Tournament: invite button for joined players while status is waiting
- Invite links use mode-prefixed codes (correspondence/XYZ, tournament/XYZ)
so notification "Beitreten" button navigates to the correct page
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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