feat(admin): rename series route and add tags review page

Rename /admin/series-management to /admin/series so it follows the
/admin/<section> convention; the breadcrumb's auto-derived parent link
is now a real route (was a dead /admin/series link).

Add an /admin/tags page to review pending TagSuggestions — list,
approve (creates the Tag), reject — backed by new admin endpoints and a
tagSuggestionReviewSchema. Resolves the dead /admin/tags alert link.

app/pages/admin/series/create.vue

@@ -1,7 +1,7 @@
 <template>
   <div class="create-form">
     <div class="page-header">
-      <NuxtLink to="/admin/series-management" class="back-link">&larr; Series</NuxtLink>
+      <NuxtLink to="/admin/series" class="back-link">&larr; Series</NuxtLink>
       <h1>Create New Series</h1>
       <p>Create a new event series to group related events together</p>
     </div>
@@ -98,7 +98,7 @@
         <!-- Form Actions -->
         <div class="form-actions">
           <NuxtLink
-            to="/admin/series-management"
+            to="/admin/series"
             class="btn"
           >
             Cancel
@@ -211,7 +211,7 @@ const createSeries = async (redirectAfter = true) => {
 
     if (redirectAfter) {
       setTimeout(() => {
-        router.push('/admin/series-management')
+        router.push('/admin/series')
       }, 1500)
     }