feat: Phase 2 UX Polish — theme system, config profiles, error banner, tests

- Add Theme struct with 3 predefined themes (dark/light/druntime)
- Add Profile struct for named configuration profiles
- Add ErrorBanner with severity levels and auto-dismiss
- Add unit tests for theme, error banner, and models
- Update CHANGELOG.md and PROJECT_STATE.md

test/tui/theme_test.go

@@ -0,0 +1,71 @@
+package tui_test
+
+import (
+	"testing"
+
+	"git.tukangketik.id/swanadiva/hostkeeper/pkg/tui"
+)
+
+func TestGetTheme(t *testing.T) {
+	// Test getting existing themes
+	tests := []struct {
+		name     string
+		expected string
+	}{
+		{"dark", "dark"},
+		{"light", "light"},
+		{"dracula", "dracula"},
+	}
+
+	for _, tt := range tests {
+		theme := tui.GetTheme(tt.name)
+		if theme.Name != tt.expected {
+			t.Errorf("GetTheme(%q) = %q, want %q", tt.name, theme.Name, tt.expected)
+		}
+	}
+
+	// Test getting non-existing theme defaults to dark
+	theme := tui.GetTheme("nonexistent")
+	if theme.Name != "dark" {
+		t.Errorf("GetTheme(nonexistent) = %q, want %q", theme.Name, "dark")
+	}
+}
+
+func TestSetTheme(t *testing.T) {
+	// Set theme to light
+	tui.SetTheme("light")
+	active := tui.GetActiveTheme()
+	if active.Name != "light" {
+		t.Errorf("After SetTheme(light), GetActiveTheme() = %q, want %q", active.Name, "light")
+	}
+
+	// Set theme back to dark
+	tui.SetTheme("dark")
+	active = tui.GetActiveTheme()
+	if active.Name != "dark" {
+		t.Errorf("After SetTheme(dark), GetActiveTheme() = %q, want %q", active.Name, "dark")
+	}
+}
+
+func TestGetActiveTheme(t *testing.T) {
+	// Default should be dark
+	active := tui.GetActiveTheme()
+	if active.Name != "dark" {
+		t.Errorf("GetActiveTheme() = %q, want %q", active.Name, "dark")
+	}
+}
+
+func TestThemeRegistry(t *testing.T) {
+	// Test that all themes are registered
+	expectedThemes := []string{"dark", "light", "dracula"}
+	for _, name := range expectedThemes {
+		if _, ok := tui.Themes[name]; !ok {
+			t.Errorf("Theme %q not found in Themes map", name)
+		}
+	}
+
+	// Test theme count
+	if len(tui.Themes) != 3 {
+		t.Errorf("Themes map has %d entries, want 3", len(tui.Themes))
+	}
+}