fix(app): iOS HIG Phase 5 — glass button system & .touch-target utility

- Add responsive glass-button-sm: 44px min-height on mobile (≤768px)
- Replace !h-7 !min-h-0 overrides with responsive min-h-[44px] md:min-h-0
- Add .touch-target utility class (44px min, inline-flex centered)
- Refactor 21 icon buttons to use .touch-target class

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="min-w-[44px] min-h-[44px] flex items-center justify-center rounded-lg transition-colors"
+          class="touch-target rounded-lg transition-colors"
           :class="isDark
             ? 'text-white/70 hover:bg-white/10'
             : 'text-gray-500 hover:bg-black/5'"