Phase 0: remove auto-updater, pin Go 1.27.1, fix vet warnings, tidy ignores

- Delete BinaryUpdate, internal/up2date, GitHub/Update structs and the
  xteveAutoUpdate / update.url settings (UI rows, en.json, defaults).
  Settings-schema migrations kept and moved to src/migrate.go.
- Drop kardianos/osext dependency.
- xteve.go version 0200 -> 0201 to match changelog; Drone now fails on drift.
- go.mod go 1.27.1; Dockerfile and Drone golang images pinned to 1.27.1.
- Fix four go vet unreachable-code warnings.
- .gitignore: .gocache/, agent.md, skill.md. .dockerignore: build context
  no longer includes caches, ts/, tasks/ or markdown except the changelog.
- Drone: publish :latest only from master; other branches publish a
  branch-named tag so a feature push cannot replace the deployed image.
- Add tasks/improvement-plan.md and tasks/todo.md.
- Regenerate src/webUI.go.

src/config.go

@@ -57,11 +57,6 @@ func Init() (err error) {
 	// Default Logeinträge, wird später von denen aus der settings.json überschrieben. Muss gemacht werden, damit die ersten Einträge auch im Log (webUI aangezeigt werden)
 	Settings.LogEntriesRAM = 500
 
-	// Variablen für den Update Prozess
-	//System.Update.Git = "https://github.com/xteve-project/xTeVe-Downloads/blob"
-	System.Update.Git = fmt.Sprintf("https://github.com/%s/%s/blob", System.GitHub.User, System.GitHub.Repo)
-	System.Update.Name = "xteve_2"
-
 	// Ordnerpfade festlegen
 	var tempFolder = os.TempDir() + string(os.PathSeparator) + System.AppName + string(os.PathSeparator)
 	tempFolder = getPlatformPath(strings.Replace(tempFolder, "//", "/", -1))
@@ -186,8 +181,7 @@ func Init() (err error) {
 		System.Branch = "master"
 	}
 
-	showInfo(fmt.Sprintf("GitHub:https://github.com/%s", System.GitHub.User))
-	showInfo(fmt.Sprintf("Git Branch:%s [%s]", System.Branch, System.GitHub.User))
+	showInfo(fmt.Sprintf("Branch:%s", System.Branch))
 
 	// Domainnamen setzten
 	setGlobalDomain(fmt.Sprintf("%s:%s", System.IPAddress, Settings.Port))