polish(design-v2): library tile pops above harbor backdrop

Surface was --color-surface (same tone as the multiplied backdrop) so
the card blended in. Switched to --color-surface-2 (lighter shade) +
stronger shadow + inset highlight so the tile clearly floats above
the harbor.

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

frontend/src/styles/design-v2.scss

@@ -157,27 +157,32 @@
 
   // Library tile becomes a single connected card — photo and Manage button
   // share the same surface, no gap between them. Manage gets a button-bar feel.
+  // Uses --color-surface-2 (lighter shade) so the card pops above the harbor
+  // multiplied backdrop that's already at --color-surface tone.
   .library__item {
-    background: var(--color-surface);
+    background: var(--color-surface-2);
     border: 1px solid var(--color-border);
     border-radius: var(--radius-md);
     overflow: hidden;
     gap: 0 !important;
-    box-shadow: 0 8px 20px -10px rgba(0,0,0,0.5);
+    box-shadow:
+      0 1px 0 color-mix(in srgb, var(--color-text) 10%, transparent) inset,
+      0 12px 28px -8px rgba(0,0,0,0.55);
     backdrop-filter: saturate(160%) blur(20px);
     -webkit-backdrop-filter: saturate(160%) blur(20px);
   }
   .library__thumb {
     border-radius: 0 !important;
+    background: var(--color-surface-2);
   }
   .library__manage {
-    background: rgba(0,0,0,0.25) !important;
+    background: rgba(0,0,0,0.35) !important;
     border-top: 1px solid var(--color-border);
     border-radius: 0 !important;
     padding: var(--space-3) var(--space-4) !important;
     transition: background var(--duration-fast) var(--ease-out);
 
-    &:hover { background: rgba(0,0,0,0.4) !important; }
+    &:hover { background: rgba(0,0,0,0.5) !important; }
   }
   .library__manage-summary {
     color: var(--color-text-muted);