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/models_test.go

@@ -0,0 +1,80 @@
+package errors_test
+
+import (
+	"testing"
+
+	"git.tukangketik.id/swanadiva/hostkeeper/internal/models"
+)
+
+func TestDefaultConfig(t *testing.T) {
+	config := models.DefaultConfig()
+
+	if config.Version != "1.0.0" {
+		t.Errorf("Version = %q, want %q", config.Version, "1.0.0")
+	}
+	if config.DefaultPort != 22 {
+		t.Errorf("DefaultPort = %d, want 22", config.DefaultPort)
+	}
+	if config.ConnectionTimeout != 30 {
+		t.Errorf("ConnectionTimeout = %d, want 30", config.ConnectionTimeout)
+	}
+	if config.Theme != "dark" {
+		t.Errorf("Theme = %q, want %q", config.Theme, "dark")
+	}
+	if len(config.Profiles) != 1 {
+		t.Errorf("Profiles has %d items, want 1", len(config.Profiles))
+	}
+	if config.ActiveProfile != "default" {
+		t.Errorf("ActiveProfile = %q, want %q", config.ActiveProfile, "default")
+	}
+}
+
+func TestAppConfigProfiles(t *testing.T) {
+	config := models.DefaultConfig()
+
+	// Test GetProfile
+	profile := config.GetProfile("default")
+	if profile == nil {
+		t.Fatal("GetProfile(default) returned nil")
+	}
+	if profile.Name != "default" {
+		t.Errorf("Profile.Name = %q, want %q", profile.Name, "default")
+	}
+
+	// Test GetProfile for non-existent profile
+	profile = config.GetProfile("nonexistent")
+	if profile != nil {
+		t.Error("GetProfile(nonexistent) should return nil")
+	}
+
+	// Test GetActiveProfile
+	profile = config.GetActiveProfile()
+	if profile == nil {
+		t.Fatal("GetActiveProfile() returned nil")
+	}
+	if profile.Name != "default" {
+		t.Errorf("Active profile Name = %q, want %q", profile.Name, "default")
+	}
+
+	// Test AddProfile
+	newProfile := models.Profile{
+		Name:  "work",
+		Theme: "light",
+	}
+	config.AddProfile(newProfile)
+	if len(config.Profiles) != 2 {
+		t.Errorf("After AddProfile, Profiles has %d items, want 2", len(config.Profiles))
+	}
+
+	// Test RemoveProfile
+	config.RemoveProfile("work")
+	if len(config.Profiles) != 1 {
+		t.Errorf("After RemoveProfile, Profiles has %d items, want 1", len(config.Profiles))
+	}
+
+	// Test RemoveProfile for non-existent profile
+	config.RemoveProfile("nonexistent")
+	if len(config.Profiles) != 1 {
+		t.Errorf("After RemoveProfile(nonexistent), Profiles has %d items, want 1", len(config.Profiles))
+	}
+}