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.

xteve.go

@@ -16,31 +16,12 @@ import (
 	"xteve/src"
 )
 
-// GitHubStruct : GitHub Account. Über diesen Account werden die Updates veröffentlicht
-type GitHubStruct struct {
-	Branch string
-	Repo   string
-	Update bool
-	User   string
-}
-
-// GitHub : GitHub Account
-// If you want to fork this project, enter your Github account here. This prevents a newer version of xTeVe from updating your version.
-var GitHub = GitHubStruct{Branch: "master", User: "xteve-project", Repo: "xTeVe-Downloads", Update: true}
-
-/*
-	Branch: GitHub Branch
-	User: 	GitHub Username
-	Repo: 	GitHub Repository
-	Update: Automatic updates from the GitHub repository [true|false]
-*/
-
 // Name : Programmname
 const Name = "xTeVe"
 
 // Version : Version, die Build Nummer wird in der main func geparst.
 // Can be overwritten at build time: -ldflags "-X main.Version=..."
-var Version = "2.2.0.0200"
+var Version = "2.2.0.0201"
 
 // DBVersion : Datanbank Version
 const DBVersion = "2.1.0"
@@ -71,10 +52,8 @@ func main() {
 
 	var system = &src.System
 	system.APIVersion = APIVersion
-	system.Branch = GitHub.Branch
 	system.Build = build[len(build)-1:][0]
 	system.DBVersion = DBVersion
-	system.GitHub = GitHub
 	system.Name = Name
 	system.Version = strings.Join(build[0:len(build)-1], ".")
 
@@ -188,11 +167,6 @@ func main() {
 		os.Exit(0)
 	}
 
-	err = src.BinaryUpdate()
-	if err != nil {
-		src.ShowError(err, 0)
-	}
-
 	err = src.StartSystem(false)
 	if err != nil {
 		src.ShowError(err, 0)