fix: expand cell padding in print layout to fit 6 bills per A4 page

Increase padding and spacing to fit exactly 6 bills per page (down from 8).
- Increase table cell padding (th: 8px 12px, td: 16px 12px)
- Set barcode image max-height to 85px
- Increase text spacing to 0.5rem in print mode

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/ui/PrintPreview.tsx

@@ -40,7 +40,7 @@ export const PrintPreview: React.FC<PrintPreviewProps> = ({ data, year, month, t
             width: 69.6mm !important;
             max-width: 69.6mm !important;
             height: auto !important;
-            max-height: none !important;
+            max-height: 85px !important;
           }
 
           .print-table {
@@ -70,9 +70,21 @@ export const PrintPreview: React.FC<PrintPreviewProps> = ({ data, year, month, t
             background: white !important;
           }
 
+          .print-table th {
+            padding: 8px 12px !important;
+          }
+
+          .print-table td {
+            padding: 16px 12px !important;
+          }
+
           .print-table thead tr {
             background: #f5f5f5 !important;
           }
+
+          .print-table .space-y-1 > * + * {
+            margin-top: 0.5rem !important;
+          }
         }
       `}</style>