feat: board-first orchestration with Gateway Bridge, live-update, and flow-board

- GatewayBridgeController: MCP-artiger Kommando-Adapter für Agent-zu-Backend
- TaskBridgeService + LiveUpdateService: SSE Live-Sync + Bridge-Kommandos
- FlowBoard.vue: Board-first orchestration dashboard panel
- live-sync.ts store + live.ts service: SSE-basierte Live-Updates
- Nullability-Warnung in HealthController.cs gefixt
- nginx.conf: SSE-Proxy + CORS für Bridge-Endpunkte
- .gitignore: pnpm/corepack local caches ausgeschlossen
- docs: architecture-board-first-orchestration.md hinzugefügt
- README: Backend Bridge API dokumentiert

frontend/nginx.conf

@@ -24,8 +24,37 @@ server {
         add_header Expires "0";
     }
 
+    # Bridge-Endpunkte (Agent-zu-Backend): separater Pfad ohne CSP-Einschränkungen
+    # für Gateway-Calls. Kein Caching, kein Buffering.
+    location /api/bridge/ {
+        proxy_pass http://api:8080;
+        proxy_set_header Host $host;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+        proxy_set_header X-Agent-Id $http_x_agent_id;
+        proxy_buffering off;
+        proxy_read_timeout 120s;
+    }
+
+    # Dashboard SSE stream: single dedicated non-buffered block.
+    location = /api/dashboard/live {
+        proxy_pass http://api:8080;
+        proxy_http_version 1.1;
+        proxy_set_header Connection "";
+        proxy_set_header Host $host;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+        proxy_buffering off;
+        proxy_cache off;
+        proxy_read_timeout 1h;
+        proxy_send_timeout 1h;
+        add_header Cache-Control "no-cache, no-store, must-revalidate" always;
+        add_header X-Accel-Buffering no always;
+    }
+
     location /api/ {
         proxy_pass http://api:8080;
+        proxy_http_version 1.1;
         proxy_set_header Host $host;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_set_header X-Forwarded-Proto $scheme;