Fix Nostr icon and make algo filters responsive

- Replace broken shield SVG in auth modal Nostr login button
  with a proper key icon (matches Nostr's key-based identity)
- Show algorithm filter buttons inline on xl+ screens (1280px+)
  where there's room for all of them
- Collapse into "Algos" dropdown on md–xl screens to prevent
  overflow when the header is too narrow

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

src/components/AppHeader.vue

@@ -13,8 +13,19 @@
             <button @click="handleFilmsClick" :class="isRoute('/') && !activeAlgorithm ? 'nav-button-active' : 'nav-button'">Films</button>
             <router-link to="/library" :class="isRoute('/library') && !activeAlgorithm ? 'nav-button-active' : 'nav-button'" @click="clearFilter">My List</router-link>
 
-            <!-- Algos Dropdown -->
-            <div class="relative algos-dropdown">
+            <!-- Inline Algorithm Buttons (xl+ screens where they fit) -->
+            <button
+              v-for="algo in algorithms"
+              :key="'inline-' + algo.id"
+              @click="handleAlgoSelect(algo.id)"
+              :class="activeAlgorithm === algo.id ? 'nav-button-active' : 'nav-button'"
+              class="hidden xl:inline-block"
+            >
+              {{ algo.label }}
+            </button>
+
+            <!-- Algos Dropdown (md–xl screens where inline buttons would overflow) -->
+            <div class="relative algos-dropdown xl:hidden">
               <button
                 @click="toggleAlgosMenu"
                 :class="activeAlgorithm ? 'nav-button-active' : 'nav-button'"
@@ -29,7 +40,7 @@
                   <div class="px-3 py-1 text-xs text-white/40 uppercase tracking-wider">Discovery Algorithms</div>
                   <button
                     v-for="algo in algorithms"
-                    :key="algo.id"
+                    :key="'dropdown-' + algo.id"
                     @click="handleAlgoSelect(algo.id)"
                     class="profile-menu-item flex items-center justify-between px-4 py-2.5 w-full text-left"
                   >