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/layout/AppSidebar.vue

@@ -67,8 +67,8 @@ function handleNav(key: string) {
 
 <template>
   <aside class="sidebar">
-    <div class="sidebar-logo" @click="router.push('/')">
-      <img src="/assets/logo.png" alt="Hermes" class="logo-img" />
+    <div class="sidebar-logo" @click="router.push('/chat')">
+      <img src="/logo.png" alt="Hermes" class="logo-img" />
       <span class="logo-text">Hermes</span>
       <canvas ref="canvasRef" class="logo-dance" />
     </div>