Add Share to L2 button for effects

- Add /effects/{cid}/publish endpoint to publish effects to L2
- Add Share to L2 button to effects detail page

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

app/templates/effects/detail.html

@@ -141,6 +141,12 @@
 
     <!-- Actions -->
     <div class="flex items-center space-x-4 mt-8">
+        <button hx-post="/effects/{{ effect.cid }}/publish"
+                hx-target="#share-result"
+                class="bg-blue-600 hover:bg-blue-700 px-4 py-2 rounded font-medium">
+            Share to L2
+        </button>
+        <span id="share-result"></span>
         <button onclick="deleteEffect('{{ effect.cid }}')"
                 class="bg-red-600 hover:bg-red-700 px-4 py-2 rounded font-medium">
             Delete