Incorporate art-dag-mono repo into artdag/ subfolder

Merges full history from art-dag/mono.git into the monorepo
under the artdag/ directory. Contains: core (DAG engine),
l1 (Celery rendering server), l2 (ActivityPub registry),
common (shared templates/middleware), client (CLI), test (e2e).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

git-subtree-dir: artdag
git-subtree-mainline: 1a179de547
git-subtree-split: 4c2e716558

artdag/l2/docker-stack.yml

@@ -0,0 +1,91 @@
+version: "3.8"
+
+# Full Art DAG stack for Docker Swarm deployment
+# Deploy with: docker stack deploy -c docker-stack.yml artdag
+
+services:
+  # Redis for L1
+  redis:
+    image: redis:7-alpine
+    volumes:
+      - redis_data:/data
+    networks:
+      - artdag
+    deploy:
+      replicas: 1
+      placement:
+        constraints:
+          - node.role == manager
+      restart_policy:
+        condition: on-failure
+
+  # L1 Server (API)
+  l1-server:
+    image: git.rose-ash.com/art-dag/l1-server:latest
+    ports:
+      - "8100:8100"
+    env_file:
+      - .env
+    environment:
+      - REDIS_URL=redis://redis:6379/5
+      - CACHE_DIR=/data/cache
+      # L1_PUBLIC_URL, L2_SERVER, L2_DOMAIN from .env file
+    volumes:
+      - l1_cache:/data/cache
+    depends_on:
+      - redis
+    networks:
+      - artdag
+    deploy:
+      replicas: 1
+      restart_policy:
+        condition: on-failure
+
+  # L1 Worker (Celery)
+  l1-worker:
+    image: git.rose-ash.com/art-dag/l1-server:latest
+    command: celery -A celery_app worker --loglevel=info
+    environment:
+      - REDIS_URL=redis://redis:6379/5
+      - CACHE_DIR=/data/cache
+      - C_FORCE_ROOT=true
+    volumes:
+      - l1_cache:/data/cache
+    depends_on:
+      - redis
+    networks:
+      - artdag
+    deploy:
+      replicas: 2
+      restart_policy:
+        condition: on-failure
+
+  # L2 Server (ActivityPub)
+  l2-server:
+    image: git.rose-ash.com/art-dag/l2-server:latest
+    ports:
+      - "8200:8200"
+    env_file:
+      - .env
+    environment:
+      - ARTDAG_DATA=/data/l2
+      # ARTDAG_DOMAIN, JWT_SECRET from .env file (multi-actor, no ARTDAG_USER)
+    volumes:
+      - l2_data:/data/l2
+    depends_on:
+      - l1-server
+    networks:
+      - artdag
+    deploy:
+      replicas: 1
+      restart_policy:
+        condition: on-failure
+
+volumes:
+  redis_data:
+  l1_cache:
+  l2_data:
+
+networks:
+  artdag:
+    driver: overlay