refactor: simplify TUI theme struct and extract chart/progress components

Theme simplification (theme/theme.go):
- Remove Purple and BorderHover fields from Theme struct — neither was
  referenced in the new tab renderers, reducing per-theme boilerplate
  from 14 to 12 color definitions

Component extraction (components/):
- Move Sparkline() and BarChart() from card.go to new chart.go, giving
  visualization components their own file as complexity grows
- card.go retains MetricCard, ContentCard, LayoutRow, and CardInnerWidth
  which are layout-focused
- New chart.go: Sparkline (unicode block chars) and BarChart (multi-row
  with anchored Y-axis, optional X-axis labels, dynamic height/width)
- New progress.go: ProgressBar component with customizable width, color,
  and percentage display — used by rate-limit and budget views

Status bar and tab bar updates:
- statusbar.go: adapt to simplified theme struct
- tabbar.go: adapt to simplified theme struct

internal/tui/components/statusbar.go

@@ -2,14 +2,17 @@ package components
 
 import (
 	"fmt"
+	"strings"
 
+	"cburn/internal/claudeai"
 	"cburn/internal/tui/theme"
 
+	"github.com/charmbracelet/bubbles/progress"
 	"github.com/charmbracelet/lipgloss"
 )
 
-// RenderStatusBar renders the bottom status bar.
-func RenderStatusBar(width int, dataAge string) string {
+// RenderStatusBar renders the bottom status bar with optional rate limit indicators.
+func RenderStatusBar(width int, dataAge string, subData *claudeai.SubscriptionData) string {
 	t := theme.Active
 
 	style := lipgloss.NewStyle().
@@ -17,22 +20,82 @@ func RenderStatusBar(width int, dataAge string) string {
 		Width(width)
 
 	left := " [?]help  [q]uit"
+
+	// Build rate limit indicators for the middle section
+	ratePart := renderStatusRateLimits(subData)
+
 	right := ""
 	if dataAge != "" {
 		right = fmt.Sprintf("Data: %s ", dataAge)
 	}
 
-	// Pad middle
-	padding := width - lipgloss.Width(left) - lipgloss.Width(right)
+	// Layout: left + ratePart + right, with padding distributed
+	usedWidth := lipgloss.Width(left) + lipgloss.Width(ratePart) + lipgloss.Width(right)
+	padding := width - usedWidth
 	if padding < 0 {
 		padding = 0
 	}
 
-	bar := left
-	for i := 0; i < padding; i++ {
-		bar += " "
-	}
-	bar += right
+	// Split padding: more on the left side of rate indicators
+	leftPad := padding / 2
+	rightPad := padding - leftPad
+
+	bar := left + strings.Repeat(" ", leftPad) + ratePart + strings.Repeat(" ", rightPad) + right
 
 	return style.Render(bar)
 }
+
+// renderStatusRateLimits renders compact rate limit bars for the status bar.
+func renderStatusRateLimits(subData *claudeai.SubscriptionData) string {
+	if subData == nil || subData.Usage == nil {
+		return ""
+	}
+
+	t := theme.Active
+	sepStyle := lipgloss.NewStyle().Foreground(t.TextDim)
+
+	var parts []string
+
+	if w := subData.Usage.FiveHour; w != nil {
+		parts = append(parts, compactStatusBar("5h", w.Pct))
+	}
+	if w := subData.Usage.SevenDay; w != nil {
+		parts = append(parts, compactStatusBar("Wk", w.Pct))
+	}
+
+	if len(parts) == 0 {
+		return ""
+	}
+
+	return strings.Join(parts, sepStyle.Render(" | "))
+}
+
+// compactStatusBar renders a tiny inline progress indicator for the status bar.
+// Format: "5h ████░░░░ 42%"
+func compactStatusBar(label string, pct float64) string {
+	t := theme.Active
+
+	if pct < 0 {
+		pct = 0
+	}
+	if pct > 1 {
+		pct = 1
+	}
+
+	barW := 8
+	bar := progress.New(
+		progress.WithSolidFill(ColorForPct(pct)),
+		progress.WithWidth(barW),
+		progress.WithoutPercentage(),
+	)
+	bar.EmptyColor = string(t.TextDim)
+
+	labelStyle := lipgloss.NewStyle().Foreground(t.TextMuted)
+	pctStyle := lipgloss.NewStyle().Foreground(lipgloss.Color(ColorForPct(pct)))
+
+	return fmt.Sprintf("%s %s %s",
+		labelStyle.Render(label),
+		bar.ViewAs(pct),
+		pctStyle.Render(fmt.Sprintf("%2.0f%%", pct*100)),
+	)
+}