fix(app): iOS HIG Phase 4 — tab bar, gaps, and grid card audit

- ContentPanel: tab gap-1→gap-2, tab buttons min-h-[44px], close button 44px
- Audited all gap-0.5/gap-1: all remaining are between non-interactive elements
- Audited all grid card buttons: no undersized action buttons found

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

packages/app/src/components/content/ContentPanel.vue

@@ -19,7 +19,7 @@
           {{ panelTitle }}
         </h3>
         <button
-          class="p-2 rounded-lg transition-colors"
+          class="min-w-[44px] min-h-[44px] flex items-center justify-center rounded-lg transition-colors"
           :class="isDark
             ? 'text-white/70 hover:bg-white/10'
             : 'text-gray-500 hover:bg-black/5'"
@@ -34,12 +34,12 @@
       <!-- Tab bar (when multiple tabs available) -->
       <div
         v-if="displayTabs.length > 1 && !hasDetailOpen"
-        class="flex items-center gap-1 px-3 pt-3 pb-1 shrink-0 overflow-x-auto scrollbar-hide"
+        class="flex items-center gap-2 px-3 pt-3 pb-1 shrink-0 overflow-x-auto scrollbar-hide"
       >
         <button
           v-for="tab in displayTabs"
           :key="tab"
-          class="text-xs px-2.5 py-1.5 rounded-lg font-medium whitespace-nowrap transition-all duration-150"
+          class="text-xs px-2.5 min-h-[44px] flex items-center justify-center rounded-lg font-medium whitespace-nowrap transition-all duration-150"
           :class="activeTab === tab
             ? 'nav-tab-active'
             : isDark