fix(tui): force TrueColor profile for consistent background rendering

Set lipgloss.SetColorProfile(termenv.TrueColor) before launching the
Bubble Tea program to ensure ANSI escape codes are always generated
for background styling.

Without this fix, lipgloss may default to the Ascii profile on some
terminals, causing all background colors to be stripped. This manifests
as cards with missing backgrounds and inconsistent visual appearance
where borders render but fills don't.

This is particularly important for the visual polish work where
components like cards, status bars, and tab bars rely heavily on
background colors to create depth and visual hierarchy.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cmd/tui.go

@@ -8,6 +8,8 @@ import (
 	"github.com/theirongolddev/cburn/internal/tui/theme"
 
 	tea "github.com/charmbracelet/bubbletea"
+	"github.com/charmbracelet/lipgloss"
+	"github.com/muesli/termenv"
 	"github.com/spf13/cobra"
 )
 
@@ -26,6 +28,10 @@ func runTUI(_ *cobra.Command, _ []string) error {
 	cfg, _ := config.Load()
 	theme.SetActive(cfg.Appearance.Theme)
 
+	// Force TrueColor profile so all background styling produces ANSI codes
+	// Without this, lipgloss may default to Ascii profile (no colors)
+	lipgloss.SetColorProfile(termenv.TrueColor)
+
 	app := tui.NewApp(flagDataDir, flagDays, flagProject, flagModel, !flagNoSubagents)
 	p := tea.NewProgram(app, tea.WithAltScreen())