feat(backend): guest-facing Wahl result endpoint

GET /api/wahl/guest/results (guest JWT) returns, per Wahl the guest took
part in, their assignment: status PENDING (algorithm not run yet) /
ASSIGNED (workshopName + wunschRang) / UNASSIGNED (no capacity left).
Verified both PENDING and ASSIGNED paths against local Postgres.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/src/wahl/wahl.controller.ts

@@ -78,6 +78,14 @@ export class WahlController {
     return this.wahl.guestOverview(guest.kcId, guest.guestId);
   }
 
+  /// The guest's own assignment result per Wahl they took part in.
+  @Get('guest/results')
+  @UseGuards(AuthGuard('guest'))
+  guestResults(@Req() req: GuestAuthenticatedRequest) {
+    const guest = req.user!;
+    return this.wahl.guestResults(guest.kcId, guest.guestId);
+  }
+
   /// Guests submit their own workshop preferences (guest JWT, not Authentik).
   @Post(':wahlId/teilnehmer')
   @UseGuards(AuthGuard('guest'))