Ideas: add reopen button when awaiting; add /reopen endpoint

site/src/components/IdeasPage.svelte

@@ -184,6 +184,21 @@
     return s === 'awaiting' ? 0 : s === 'done' ? 2 : s === 'declined' ? 3 : 1;
   }
 
+  async function reopenIdea(idea: Idea) {
+    const r = await fetch(`/api/ideas/${idea.id}/reopen`, {
+      method: 'POST',
+      credentials: 'include',
+    });
+    if (r.ok) {
+      idea.status = 'open';
+      ideas = [...ideas].sort((a, b) =>
+        statusOrder(a.status) - statusOrder(b.status) ||
+        b.vote_count - a.vote_count ||
+        b.created_at - a.created_at
+      );
+    }
+  }
+
   async function declineIdea(idea: Idea) {
     const r = await fetch(`/api/ideas/${idea.id}/decline`, {
       method: 'POST',
@@ -408,6 +423,14 @@
                   style="color: {btnColor}; border: 1px solid {borderColor}"
                   title="Cycle status"
                 >{nextLabel}</button>
+                {#if awaiting}
+                  <button
+                    on:click={() => reopenIdea(idea)}
+                    class="text-xs px-1.5 py-0.5 rounded transition-colors"
+                    style="color: var(--text-5); border: 1px solid var(--border-sub)"
+                    title="Back to todo"
+                  >↩</button>
+                {/if}
                 <button
                   on:click={() => declineIdea(idea)}
                   class="text-xs px-1.5 py-0.5 rounded transition-colors"