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/app/templates/home.html

@@ -0,0 +1,42 @@
+{% extends "base.html" %}
+
+{% block title %}Art-DAG{% endblock %}
+
+{% block content %}
+<div class="max-w-4xl mx-auto">
+    {% if readme_html %}
+    <div class="prose prose-invert max-w-none mb-12">
+        {{ readme_html | safe }}
+    </div>
+    {% else %}
+    <div class="text-center py-12">
+        <h1 class="text-4xl font-bold mb-4">Art-DAG</h1>
+        <p class="text-xl text-gray-400 mb-8">Content-Addressable Media with ActivityPub Federation</p>
+
+        {% if not user %}
+        <div class="flex justify-center space-x-4">
+            <a href="/auth/login" class="bg-gray-700 hover:bg-gray-600 px-6 py-3 rounded-lg font-medium">Login</a>
+            <a href="/auth/register" class="bg-blue-600 hover:bg-blue-700 px-6 py-3 rounded-lg font-medium">Register</a>
+        </div>
+        {% endif %}
+    </div>
+    {% endif %}
+
+    {% if activities %}
+    <h2 class="text-2xl font-bold mb-4">Recent Activity</h2>
+    <div class="space-y-4">
+        {% for activity in activities %}
+        <div class="bg-gray-800 rounded-lg p-4">
+            <div class="flex items-center justify-between mb-2">
+                <span class="text-blue-400">{{ activity.actor }}</span>
+                <span class="text-gray-500 text-sm">{{ activity.created_at }}</span>
+            </div>
+            <div class="text-gray-300">
+                {{ activity.type }}: {{ activity.summary or activity.object_type }}
+            </div>
+        </div>
+        {% endfor %}
+    </div>
+    {% endif %}
+</div>
+{% endblock %}