Add Share to L2 buttons for media, recipes, and runs

- Updated cache detail button from "Publish to IPFS" to "Share to L2"
- Added Share to L2 button on recipe detail page
- Added Share to L2 button on run detail page
- Created /recipes/{id}/publish endpoint
- Created /runs/{id}/publish endpoint (publishes run output)

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

app/templates/cache/detail.html

@@ -97,14 +97,12 @@
            class="bg-blue-600 hover:bg-blue-700 px-4 py-2 rounded font-medium">
             Download
         </a>
-        {% if not cache.ipfs_cid %}
         <button hx-post="/cache/{{ cache.content_hash }}/publish"
-                hx-target="#publish-result"
-                class="bg-gray-700 hover:bg-gray-600 px-4 py-2 rounded font-medium">
-            Publish to IPFS
+                hx-target="#share-result"
+                class="bg-purple-600 hover:bg-purple-700 px-4 py-2 rounded font-medium">
+            Share to L2
         </button>
-        <span id="publish-result"></span>
-        {% endif %}
+        <span id="share-result"></span>
     </div>
 </div>
 {% endblock %}