fix(home): card fills the slide; preview uses photo's natural aspect

Two complaints, one root cause: the FrameCard was floating in the slide with
a min-height-padded preview, so (1) photos got top/bottom gray bars instead
of fitting their container, and (2) there was a fat empty gap between the
card body and the bottom nav.

Restructured the large card to flex-fill its slide:
- preview hugs the photo's intrinsic aspect ratio (img with width:100%
  height:auto); no min-height, no aspect-ratio override → no letterbox
- card body has flex:1, info pinned at top, Add Photo button pinned at
  bottom via margin-top:auto and width:100%
- HomeView main / single-card / carousel all flex:1 down through the
  layout so the slide gets the full available height
- empty-state placeholder still reserves the device's aspect so the
  card doesn't jump while images load

Result: the photo fills its container left/right with no bars; the body
absorbs all remaining space below, with the action button always sitting
just above the bottom nav.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

public/build/index.html

@@ -14,7 +14,7 @@
     <meta name="mobile-web-app-capable" content="yes" />
     <meta name="apple-mobile-web-app-status-bar-style" content="default" />
     <meta name="apple-mobile-web-app-title" content="pictureFrame" />
-    <script type="module" crossorigin src="/build/assets/index-BxH1sIci.js"></script>
+    <script type="module" crossorigin src="/build/assets/index-aP_uBWCi.js"></script>
     <link rel="modulepreload" crossorigin href="/build/assets/_plugin-vue_export-helper-DVo1OUMD.js">
     <link rel="stylesheet" crossorigin href="/build/assets/index-BlLBHR1q.css">
   </head>