Add a shop sales dashboard with 30-day charts (#8)

## Summary
- Closes #7
- Portal Retail **Sales** page: 30-day orders/revenue/units/AOV, daily charts, top products
- Home dashboard cards for 30-day shop sales and revenue when `FEATURE_SHOP` is on
- Stacks on #6 (shop catalog). Merge that first, then retarget `master` if needed.

## Test plan
- [ ] Sales page requires login; empty state with no paid orders
- [ ] Paid/fulfilled in the last 30 days counted; draft/open/cancelled/old excluded
- [ ] Top products ranked by units; home dashboard shows 30-day sales count
- [ ] `manage.py test shop core.tests_features`

Reviewed-on: #8

site/client_site/static/css/portal.css

@@ -264,6 +264,63 @@ body.portal {
   line-height: 1.2;
   white-space: nowrap;
 }
+.chart-placeholder.chart-daily {
+  gap: 3px;
+  padding: 16px 10px 8px;
+  overflow-x: auto;
+}
+.chart-placeholder.chart-daily .chart-bar-col {
+  flex: 1 0 8px;
+  min-width: 6px;
+}
+.chart-placeholder.chart-daily .chart-bar-col .bar {
+  min-height: 0;
+}
+.chart-placeholder.chart-daily .chart-bar-col .bar.is-zero {
+  height: 0 !important;
+  min-height: 0;
+  opacity: 0.2;
+}
+.chart-placeholder.chart-daily .chart-bar-label {
+  font-size: 10px;
+}
+.chart-placeholder.chart-revenue .chart-bar-col .bar {
+  background: var(--monica-primary-light);
+}
+.hbar-chart {
+  display: flex;
+  flex-direction: column;
+  gap: 12px;
+}
+.hbar-row {
+  display: grid;
+  grid-template-columns: minmax(72px, 160px) 1fr auto;
+  gap: 12px;
+  align-items: center;
+}
+.hbar-label {
+  font-size: 13px;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+.hbar-track {
+  height: 16px;
+  background: #e8f4f5;
+  overflow: hidden;
+}
+.hbar-fill {
+  height: 100%;
+  background: var(--monica-primary);
+  opacity: 0.8;
+  min-width: 0;
+}
+.hbar-value {
+  font-size: 13px;
+  font-weight: 600;
+  min-width: 2.5ch;
+  text-align: right;
+}
 
 .consent-pills { display: flex; gap: 6px; flex-wrap: wrap; }
 .preview-pane {