feat(scanner): add Scanner.PurgeMissing configuration option (#4107)

* Initial plan for issue

* Add Scanner.PurgeMissing configuration option

Co-authored-by: deluan <331353+deluan@users.noreply.github.com>

* Remove GC call from phaseMissingTracks.purgeMissing method

Co-authored-by: deluan <331353+deluan@users.noreply.github.com>

* Address PR comments for Scanner.PurgeMissing feature

Co-authored-by: deluan <331353+deluan@users.noreply.github.com>

* Address PR comments and add DeleteAllMissing method

Co-authored-by: deluan <331353+deluan@users.noreply.github.com>

* refactor(scanner): simplify purgeMissing logic and improve error handling

Signed-off-by: Deluan <deluan@navidrome.org>

* fix configuration test

Signed-off-by: Deluan <deluan@navidrome.org>

---------

Signed-off-by: Deluan <deluan@navidrome.org>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: deluan <331353+deluan@users.noreply.github.com>
Co-authored-by: Deluan <deluan@navidrome.org>

conf/configuration_test.go

@@ -5,7 +5,7 @@ import (
 	"path/filepath"
 	"testing"
 
-	. "github.com/navidrome/navidrome/conf"
+	"github.com/navidrome/navidrome/conf"
 	. "github.com/onsi/ginkgo/v2"
 	. "github.com/onsi/gomega"
 	"github.com/spf13/viper"
@@ -20,9 +20,10 @@ var _ = Describe("Configuration", func() {
 	BeforeEach(func() {
 		// Reset viper configuration
 		viper.Reset()
+		conf.SetViperDefaults()
 		viper.SetDefault("datafolder", GinkgoT().TempDir())
 		viper.SetDefault("loglevel", "error")
-		ResetConf()
+		conf.ResetConf()
 	})
 
 	DescribeTable("should load configuration from",
@@ -30,17 +31,17 @@ var _ = Describe("Configuration", func() {
 			filename := filepath.Join("testdata", "cfg."+format)
 
 			// Initialize config with the test file
-			InitConfig(filename)
+			conf.InitConfig(filename)
 			// Load the configuration (with noConfigDump=true)
-			Load(true)
+			conf.Load(true)
 
 			// Execute the format-specific assertions
-			Expect(Server.MusicFolder).To(Equal(fmt.Sprintf("/%s/music", format)))
-			Expect(Server.UIWelcomeMessage).To(Equal("Welcome " + format))
-			Expect(Server.Tags["custom"].Aliases).To(Equal([]string{format, "test"}))
+			Expect(conf.Server.MusicFolder).To(Equal(fmt.Sprintf("/%s/music", format)))
+			Expect(conf.Server.UIWelcomeMessage).To(Equal("Welcome " + format))
+			Expect(conf.Server.Tags["custom"].Aliases).To(Equal([]string{format, "test"}))
 
 			// The config file used should be the one we created
-			Expect(Server.ConfigFile).To(Equal(filename))
+			Expect(conf.Server.ConfigFile).To(Equal(filename))
 		},
 		Entry("TOML format", "toml"),
 		Entry("YAML format", "yaml"),