Enhance UI and functionality across multiple components

- Updated styles in style.css to improve overall design consistency and introduced CSS variables for better theming.
- Refined ChatWindow.vue with improved no-conversation styling and adjusted image borders for a cleaner look.
- Enhanced HistoryView.vue and InboxView.vue with new panel styles for better user experience and readability.
- Revamped LoginForm.vue to provide a more engaging user interface with a landing page layout and cookie-based profile persistence.
- Improved MenuBar.vue and SearchView.vue with active state indicators and refined item displays for better navigation.
- Added logout functionality in chat store and server routes to manage user sessions effectively.
- Introduced a new mockup view route for design previews.

These changes collectively enhance the user experience and visual appeal of the application.

client/src/components/InboxView.vue

@@ -1,8 +1,8 @@
 <template>
   <div class="inbox-list">
-    <h2>{{ $t('menu_inbox') }}</h2>
+    <h2 class="panel-title">{{ $t('menu_inbox') }}</h2>
     
-    <div v-if="chatStore.inboxResults.length === 0">
+    <div v-if="chatStore.inboxResults.length === 0" class="panel-empty">
       <p>Keine ungelesenen Nachrichten.</p>
     </div>
     
@@ -12,7 +12,8 @@
       class="inbox-item"
       @click="selectUser(item.userName)"
     >
-      {{ item.userName }} ({{ item.unreadCount }} ungelesen)
+      <span class="panel-item-name">{{ item.userName }}</span>
+      <span class="panel-item-meta">{{ item.unreadCount }} ungelesen</span>
     </div>
   </div>
 </template>
@@ -27,3 +28,34 @@ function selectUser(userName) {
 }
 </script>
 
+<style scoped>
+.panel-title {
+  margin-bottom: 14px;
+  font-size: 18px;
+  color: #18201b;
+}
+
+.panel-empty {
+  color: #637067;
+}
+
+.inbox-item {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+  border-radius: 10px;
+}
+
+.panel-item-name {
+  font-weight: 600;
+  color: #18201b;
+}
+
+.panel-item-meta {
+  white-space: nowrap;
+  font-size: 12px;
+  font-weight: 600;
+  color: #536159;
+}
+</style>