fix: add 1-item scroll buffer and use highlight color for selected border

Scroll triggers when the next item would be off-screen, not when the
current item hits the edge. Selected border now uses highlight color
(steel blue) instead of accent (white) for visibility on all themes.

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

pkg/tui/account.go

@@ -129,13 +129,13 @@ func (m Model) scrollToAccountDetailItem() Model {
 	vpH := m.account.detailViewport.Height
 	offset := m.account.detailViewport.YOffset
 
-	// If item is above viewport, scroll up to show it
-	if targetY < offset {
-		m.account.detailViewport.SetYOffset(targetY)
+	// 1-item buffer: scroll when the NEXT item would be off-screen,
+	// not when the current item hits the very edge
+	if targetY-itemHeight < offset {
+		m.account.detailViewport.SetYOffset(targetY - itemHeight)
 	}
-	// If item is below viewport, scroll down to show it
-	if targetY+itemHeight > offset+vpH {
-		m.account.detailViewport.SetYOffset(targetY - vpH + itemHeight)
+	if targetY+itemHeight+itemHeight > offset+vpH {
+		m.account.detailViewport.SetYOffset(targetY - vpH + itemHeight + itemHeight)
 	}
 
 	return m

pkg/tui/account_orders.go

@@ -88,7 +88,7 @@ func (m Model) buildOrderCard(order models.Order, boxWidth int, isSelected bool)
 
 	var itemBox lipgloss.Style
 	if isSelected {
-		itemBox = base.BorderForeground(m.theme.Accent())
+		itemBox = base.BorderForeground(m.theme.Highlight())
 	} else {
 		itemBox = base.BorderForeground(m.theme.Border())
 	}