ui: hide Persona switcher and Extension button from header

These are dev/testing tools that shouldn't be visible in production.
Commented out for now so they can be re-enabled easily.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/components/AppHeader.vue

@@ -73,9 +73,8 @@
 
         <!-- Right Side Actions -->
         <div class="flex items-center gap-4">
-          <!-- Nostr Login (persona switcher or extension) -->
+          <!-- Nostr Login (persona switcher or extension) — hidden for now
           <div v-if="!hasNostrSession" class="hidden md:flex items-center gap-2">
-            <!-- Persona Switcher (dev) -->
             <div class="relative persona-dropdown">
               <button @click="togglePersonaMenu" class="nav-button px-3 py-2 text-xs">
                 Persona
@@ -109,12 +108,11 @@
                 </div>
               </div>
             </div>
-
-            <!-- Extension Login -->
             <button @click="handleExtensionLogin" class="nav-button px-3 py-2 text-xs">
               Extension
             </button>
           </div>
+          -->
 
           <!-- Sign In (app auth, if not Nostr logged in) -->
           <button