fix(app): iOS HIG Phase 3 — content & settings touch targets (44px minimum)

- Detail views: back buttons expanded across all 8 detail components
- SettingsModal/SettingsPanel: close, edit/delete, tab buttons expanded
- MemoryPanel: edit/delete buttons + gap fix
- PersonaSelector: close button expanded
- PluginMarketplace: settings gear button expanded
- NostrGrid: sub-tab and filter buttons expanded
- PlayerBar, MapRenderer, BranchSwitcher, ZapDialog, NostrDMs,
  NostrThread, NostrArticles, DesignSystemDetail/Grid: all remaining
  small interactive buttons expanded to 44px minimum

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

packages/app/src/components/settings/PluginMarketplace.vue

@@ -94,7 +94,7 @@
                 Update to v{{ store.updatesAvailable.get(plugin.id) }}
               </button>
               <button
-                class="text-xs p-1 rounded text-white/30 hover:text-white/60 hover:bg-white/5 transition-colors"
+                class="text-xs min-w-[44px] min-h-[44px] flex items-center justify-center rounded text-white/30 hover:text-white/60 hover:bg-white/5 transition-colors"
                 @click="editingPlugin = editingPlugin === plugin.id ? null : plugin.id"
               >
                 <svg class="w-3.5 h-3.5" fill="none" stroke="currentColor" viewBox="0 0 24 24">

packages/app/src/components/settings/SettingsPanel.vue

@@ -5,7 +5,7 @@
       <div class="p-4 border-b border-white/[0.08] flex items-center justify-between shrink-0">
         <h2 class="text-sm font-bold text-white/90">Settings</h2>
         <button
-          class="p-1.5 rounded-lg text-white/40 hover:text-white/70 hover:bg-white/5 transition-colors"
+          class="min-w-[44px] min-h-[44px] flex items-center justify-center rounded-lg text-white/40 hover:text-white/70 hover:bg-white/5 transition-colors"
           @click="$emit('close')"
         >
           <svg class="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
@@ -19,7 +19,7 @@
         <button
           v-for="tab in tabs"
           :key="tab.id"
-          class="text-xs px-2 py-1 rounded-md whitespace-nowrap transition-all duration-150"
+          class="text-xs px-3 min-h-[44px] flex items-center justify-center rounded-md whitespace-nowrap transition-all duration-150"
           :class="activeTab === tab.id
             ? 'nav-tab-active'
             : 'text-white/40 hover:text-white/70 hover:bg-white/5'"