feat(11-05): visual consistency pass — typography, focus-visible, hover/active states, skeleton cleanup

- Normalize page titles to text-2xl font-semibold (was font-bold in TopicsView, DocumentView, SharedView)
- Normalize section titles to text-lg font-semibold (was text-xl in SettingsPreferencesTab, SettingsAiTab, SettingsCloudTab, BackupCodesDisplay, CloudCredentialModal)
- Normalize panel headings to text-sm font-semibold (SettingsAccountTab, DocumentView)
- Normalize AdminOverviewView page title from text-xl to text-2xl font-semibold
- Replace decorative sidebar skeleton inline styles with static Tailwind width classes (w-12/w-16/w-20)
- Add focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-indigo-500 focus-visible:ring-offset-1 to all interactive buttons across the app
- Add active:bg-* states to primary and secondary buttons for coherent press feedback
- Update nav-link scoped CSS in AppSidebar and AdminSidebar to include active:bg-gray-200 and focus-visible ring
- Add 7 new tests: VISUAL-01 skeleton class invariant, VISUAL-04 focus-visible invariant, VISUAL-03 typography invariant (36 test files, 270 tests pass)

frontend/src/views/TopicsView.vue

@@ -3,7 +3,7 @@
     <!-- Header -->
     <div class="flex items-center justify-between mb-6">
       <div>
-        <h2 class="text-2xl font-bold text-gray-900">
+        <h2 class="text-2xl font-semibold text-gray-900">
           {{ activeTopic ? activeTopic : 'All Topics' }}
         </h2>
         <p class="text-gray-500 text-sm mt-0.5">
@@ -13,7 +13,7 @@
       <button
         v-if="activeTopic"
         @click="$router.push('/topics')"
-        class="text-sm text-indigo-600 hover:underline"
+        class="text-sm text-indigo-600 hover:underline focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-indigo-500 focus-visible:ring-offset-1 rounded"
       >
         ← All Topics
       </button>
@@ -31,7 +31,7 @@
             v-for="topic in topicsStore.topics"
             :key="topic.id"
             :to="`/topics/${encodeURIComponent(topic.name)}`"
-            class="bg-white border border-gray-200 rounded-xl p-4 hover:border-indigo-300 hover:shadow-sm transition-all"
+            class="bg-white border border-gray-200 rounded-xl p-4 hover:border-indigo-300 hover:shadow-sm transition-all focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-indigo-500 focus-visible:ring-offset-1"
           >
             <div class="flex items-center gap-2 mb-2">
               <span class="w-3 h-3 rounded-full" :style="{ backgroundColor: topic.color }"></span>