feat: add token auth, login page, skill toggle, and route restructure

- Add token-based authentication with auto-generated token stored in server/data/.token
- Add login page with URL token auto-fill support
- Add route guards requiring auth for all pages except login
- Restructure routes: / for login, /chat for conversations
- Add skill enable/disable toggle via config.yaml skills.disabled
- Unify logo to /logo.png across sidebar, login, messages, and empty state
- Hide sidebar on login page, prevent flash with router.isReady()
- Fix session export JSON parse error when CLI returns non-JSON output
- Display token in CLI on server start

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/chat/MessageList.vue

@@ -42,7 +42,7 @@ watch(currentToolCalls, scrollToBottom)
 <template>
   <div ref="listRef" class="message-list">
     <div v-if="chatStore.messages.length === 0" class="empty-state">
-      <img src="/assets/logo.png" alt="Hermes" class="empty-logo" />
+      <img src="/logo.png" alt="Hermes" class="empty-logo" />
       <p>{{ t('chat.emptyState') }}</p>
     </div>
     <MessageItem