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/l1/requirements.txt

@@ -0,0 +1,19 @@
+celery[redis]>=5.3.0
+redis>=5.0.0
+requests>=2.31.0
+httpx>=0.27.0
+itsdangerous>=2.0
+cryptography>=41.0
+fastapi>=0.109.0
+uvicorn>=0.27.0
+python-multipart>=0.0.6
+PyYAML>=6.0
+asyncpg>=0.29.0
+markdown>=3.5.0
+# Common effect dependencies (used by uploaded effects)
+numpy>=1.24.0
+opencv-python-headless>=4.8.0
+jax[cpu]>=0.4.20
+# core (artdag) and common (artdag_common) installed from local dirs in Dockerfile
+psycopg2-binary
+nest_asyncio