feat: add NATS + Dapr infrastructure for event-driven architecture

- infra/compose/nats.yml: NATS server with JetStream, persistence volume, healthcheck
- infra/compose/dapr.yml: Dapr placement service for sidecar coordination
- infra/dapr/: Dapr global config, pubsub component (NATS), statestore (Redis)
- infra/compose/scraper.yml: add Dapr sidecar container + depends_on nats/dapr
- docs/add-dapr-service.md: guide for integrating Dapr into new services
- docs/add-new-app.md: add Dapr sidecar step
- ARCHITECTURE.md: add NATS/Dapr to infra table + service mesh diagram
- infra/README.md: update layout and deployment order
- deploy-docker.yml: add nats.yml + dapr.yml to ALL_COMPOSE_FILES

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

infra/compose/dapr.yml

@@ -0,0 +1,19 @@
+services:
+  dapr-placement:
+    container_name: dapr-placement
+    image: daprio/dapr:latest
+    restart: always
+    networks:
+      - app-shared-net
+    command: ["./placement", "--port", "50005"]
+    healthcheck:
+      test: ['CMD-SHELL', 'wget --spider http://localhost:50005/healthz || exit 1']
+      interval: 15s
+      timeout: 5s
+      retries: 3
+      start_period: 10s
+
+networks:
+  app-shared-net:
+    name: app-shared-net
+    external: true