fix(app): keyboard resizes container, tab bar margin, HTTPS for PWA install

- Root container height now bound to visualViewport.height when keyboard
  is open — the whole layout shrinks instead of being pushed offscreen
- Tab bar gets 24px vertical margin (12px top + 12px bottom + safe area)
- Added @vitejs/plugin-basic-ssl for HTTPS dev server — required for PWA
  install on non-localhost origins (LAN IP access)
- Improved useVisualViewport to track fullHeight for accurate keyboard
  offset calculation across orientation changes

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

packages/app/src/pages/ChatPage.vue

@@ -309,11 +309,11 @@
       <!-- Inline player bar on mobile (above tab bar) -->
       <PlayerBar variant="inline" />
 
-      <!-- Bottom tab bar (iOS HIG: 49pt + safe area) -->
+      <!-- Bottom tab bar (iOS HIG: 49pt + safe area + 24px margin) -->
       <div
         v-show="!isKeyboardOpen"
-        class="shrink-0"
-        :style="{ paddingBottom: 'env(safe-area-inset-bottom, 0px)' }"
+        class="shrink-0 pt-3 pb-3"
+        :style="{ paddingBottom: 'calc(12px + env(safe-area-inset-bottom, 0px))' }"
       >
         <div class="flex items-center h-[49px] px-2 gap-1">
           <button