Initial artdag-common shared library

Shared components for L1 and L2 servers:
- Jinja2 template system with base template and components
- Middleware for auth and content negotiation
- Pydantic models for requests/responses
- Utility functions for pagination, media, formatting
- Constants for Tailwind/HTMX/Cytoscape CDNs

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

artdag_common/templates/components/table.html

@@ -0,0 +1,51 @@
+{#
+Table component with dark theme styling.
+
+Usage:
+    {% from "components/table.html" import table, table_row %}
+
+    {% call table(columns=["Name", "Status", "Actions"]) %}
+        {% for item in items %}
+        {{ table_row([item.name, item.status, actions_html]) }}
+        {% endfor %}
+    {% endcall %}
+#}
+
+{% macro table(columns, class="", id="") %}
+<div class="overflow-x-auto {{ class }}" {% if id %}id="{{ id }}"{% endif %}>
+    <table class="w-full text-sm">
+        <thead class="text-gray-400 border-b border-dark-600">
+            <tr>
+                {% for col in columns %}
+                <th class="text-left py-3 px-4 font-medium">{{ col }}</th>
+                {% endfor %}
+            </tr>
+        </thead>
+        <tbody class="divide-y divide-dark-600">
+            {{ caller() }}
+        </tbody>
+    </table>
+</div>
+{% endmacro %}
+
+{% macro table_row(cells, class="", href=None) %}
+<tr class="hover:bg-dark-600/50 transition-colors {{ class }}">
+    {% for cell in cells %}
+    <td class="py-3 px-4">
+        {% if href and loop.first %}
+        <a href="{{ href }}" class="text-blue-400 hover:text-blue-300">{{ cell }}</a>
+        {% else %}
+        {{ cell | safe }}
+        {% endif %}
+    </td>
+    {% endfor %}
+</tr>
+{% endmacro %}
+
+{% macro empty_row(colspan, message="No items found") %}
+<tr>
+    <td colspan="{{ colspan }}" class="py-8 text-center text-gray-400">
+        {{ message }}
+    </td>
+</tr>
+{% endmacro %}