fix: reduce card-body padding and compress owner column on mobile

- card-body padding: 16px -> 8px on mobile
- owner-td: max-width 110px, select+button stack vertically, font 11px
- Remove d-inline w-auto from owner select (was preventing compression)

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

frontend/styles.css

@@ -179,11 +179,34 @@ td.inv-col, th.inv-col {
         max-width: 120px;
     }
 
+    .card-body {
+        padding: 8px;
+    }
+
     .table td, .table th {
         font-size: 12px;
         padding: 4px 3px;
     }
 
+    .owner-td {
+        min-width: 80px;
+        max-width: 110px;
+    }
+
+    .owner-td select {
+        width: 100% !important;
+        max-width: 100%;
+        margin-bottom: 3px;
+        font-size: 11px;
+    }
+
+    .owner-td .btn {
+        width: 100%;
+        padding: 2px 4px;
+        font-size: 11px;
+        margin: 0 !important;
+    }
+
     .aud-select-bar {
         flex-direction: column !important;
         align-items: stretch !important;