feat(config/m7-363): branding config field + defaults

internal/config/config_test.go

@@ -151,3 +151,50 @@ func TestLibraryYAMLLoads(t *testing.T) {
 		t.Error("scan_on_startup = false")
 	}
 }
+
+func TestBrandingDefaults(t *testing.T) {
+	cfg := Default()
+	if cfg.Branding.AppName != "Minstrel" {
+		t.Errorf("AppName: got %q, want %q", cfg.Branding.AppName, "Minstrel")
+	}
+	if cfg.Branding.Description == "" {
+		t.Errorf("Description: empty after Default(); want default tagline")
+	}
+}
+
+func TestBrandingYAMLOverride(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "config.yaml")
+	content := []byte(`branding:
+  app_name: "Family Jukebox"
+  description: "Our home library."
+`)
+	if err := os.WriteFile(path, content, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	cfg, err := Load(path)
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if cfg.Branding.AppName != "Family Jukebox" {
+		t.Errorf("AppName: got %q", cfg.Branding.AppName)
+	}
+	if cfg.Branding.Description != "Our home library." {
+		t.Errorf("Description: got %q", cfg.Branding.Description)
+	}
+}
+
+func TestBrandingEnvOverride(t *testing.T) {
+	t.Setenv("SMARTMUSIC_BRANDING_APP_NAME", "Office Music")
+	t.Setenv("SMARTMUSIC_BRANDING_DESCRIPTION", "Office tunes.")
+	cfg, err := Load("")
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if cfg.Branding.AppName != "Office Music" {
+		t.Errorf("AppName: got %q", cfg.Branding.AppName)
+	}
+	if cfg.Branding.Description != "Office tunes." {
+		t.Errorf("Description: got %q", cfg.Branding.Description)
+	}
+}