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/MenuBar.vue

@@ -6,11 +6,18 @@
         {{ $t('menu_timeout_in', [formatTime(chatStore.remainingSecondsToTimeout)]) }}
       </span>
       <button @click="handleLeave">{{ $t('menu_leave') }}</button>
-      <button @click="handleSearch">{{ $t('menu_search') }}</button>
-      <button @click="handleInbox" :class="{ 'has-unread': chatStore.unreadChatsCount > 0 }">
+      <button @click="handleSearch" :class="{ 'is-active': chatStore.currentView === 'search' }">
+        {{ $t('menu_search') }}
+      </button>
+      <button
+        @click="handleInbox"
+        :class="{ 'has-unread': chatStore.unreadChatsCount > 0, 'is-active': chatStore.currentView === 'inbox' }"
+      >
         {{ $t('menu_inbox') }}<span v-if="chatStore.unreadChatsCount > 0"> ({{ chatStore.unreadChatsCount }})</span>
       </button>
-      <button @click="handleHistory">{{ $t('menu_history') }}</button>
+      <button @click="handleHistory" :class="{ 'is-active': chatStore.currentView === 'history' }">
+        {{ $t('menu_history') }}
+      </button>
     </template>
   </div>
 </template>
@@ -42,4 +49,3 @@ function formatTime(seconds) {
   return `${minutes}:${secs.toString().padStart(2, '0')}`;
 }
 </script>
-