feat(#195): SSE realtime Cartes (stream + emit audience)

GET /api/v1/cards/stream (Bearer ou ?access_token=).
Events card.created|updated|deleted, response.added + heartbeat.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/src/modules/cards/cards.module.ts

@@ -10,7 +10,9 @@ import { CardResponse } from 'src/entities/card_responses.entity';
 import { AmChildren } from 'src/entities/am_children.entity';
 import { ParentsChildren } from 'src/entities/parents_children.entity';
 import { CardsController } from './cards.controller';
+import { CardsRealtimeController } from './cards-realtime.controller';
 import { CardsService } from './cards.service';
+import { CardsRealtimeService } from './cards-realtime.service';
 
 @Module({
   imports: [
@@ -32,8 +34,8 @@ import { CardsService } from './cards.service';
       inject: [ConfigService],
     }),
   ],
-  controllers: [CardsController],
-  providers: [CardsService],
-  exports: [CardsService],
+  controllers: [CardsController, CardsRealtimeController],
+  providers: [CardsService, CardsRealtimeService],
+  exports: [CardsService, CardsRealtimeService],
 })
 export class CardsModule {}