Update golangci-lint to v2.12.2 with canonical config

Bump golangci-lint from v2.10.1 to v2.12.2 in the Dockerfile lint
stage (tag+digest pin) and script/bootstrap release-archive pins
(linux amd64/arm64 sha256s). Replace .golangci.yml with the canonical
v2-layout config so linter settings (lll 88, funlen 80/50, cyclop 15,
dupl 100) actually apply.

Fix all findings surfaced by the new linter and config:

- noctx: use httptest.NewRequestWithContext in all tests
- gosec G710/G703: route app redirects through a path-escaping
  redirectToApp helper; annotate internal log path usage
- goconst: introduce shared constants for template/JSON keys and
  repeated test literals
- lll: wrap lines to the 88-column limit
- dupl: extract shared helpers (generic findAllByAppID in models,
  deleteAppResource in handlers, parsePush in webhook payloads,
  table-driven/helper-based test dedup)
- nolintlint: drop nolint directives made obsolete by the new limits

Record the change in TODO.md; make check is green.

internal/service/deploy/export_test.go

@@ -26,7 +26,11 @@ func (svc *Service) CancelActiveDeploy(appID string) {
 }
 
 // RegisterActiveDeploy registers an active deploy for testing.
-func (svc *Service) RegisterActiveDeploy(appID string, cancel context.CancelFunc, done chan struct{}) {
+func (svc *Service) RegisterActiveDeploy(
+	appID string,
+	cancel context.CancelFunc,
+	done chan struct{},
+) {
 	svc.activeDeploys.Store(appID, &activeDeploy{cancel: cancel, done: done})
 }
 
@@ -41,7 +45,11 @@ func (svc *Service) UnlockApp(appID string) {
 }
 
 // NewTestServiceWithConfig creates a Service with config and docker client for testing.
-func NewTestServiceWithConfig(log *slog.Logger, cfg *config.Config, dockerClient *docker.Client) *Service {
+func NewTestServiceWithConfig(
+	log *slog.Logger,
+	cfg *config.Config,
+	dockerClient *docker.Client,
+) *Service {
 	return &Service{
 		log:    log,
 		config: cfg,