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/dapr/components/pubsub.yaml

@@ -0,0 +1,12 @@
+apiVersion: dapr.io/v1alpha1
+kind: Component
+metadata:
+  name: pubsub
+spec:
+  type: pubsub.natsstreaming
+  version: v1
+  metadata:
+    - name: natsURL
+      value: nats://nats:4222
+    - name: natsStreamingClusterID
+      value: dapr-cluster

infra/dapr/components/statestore.yaml

@@ -0,0 +1,14 @@
+apiVersion: dapr.io/v1alpha1
+kind: Component
+metadata:
+  name: statestore
+spec:
+  type: state.redis
+  version: v1
+  metadata:
+    - name: redisHost
+      value: redis:6379
+    - name: redisPassword
+      value: ""
+    - name: keyPrefix
+      value: "dapr"

infra/dapr/config.yaml

@@ -0,0 +1,13 @@
+apiVersion: dapr.io/v1alpha1
+kind: Configuration
+metadata:
+  name: dapr-config
+spec:
+  tracing:
+    samplingRate: "1"
+    zipkin:
+      endpointAddress: ""
+  metrics:
+    enabled: true
+  mtls:
+    enabled: false