chore(lint): Backlog auf 0 + golangci-lint als HARTER Gate — v1.3.3

Go-Quality-Baseline-Rollout ABGESCHLOSSEN.

Code-Quality-Backlog (55 → 0):
- errcheck: unbehandelte Close/Rollback/Remove explizit `_ =`; fmt.Sscanf
  `_, _ =` (Zero-Value degradiert sauber).
- unused: toter Code entfernt (nodeIDOrHostname, stripTrailingNewline,
  acme.Service.user, strFold + ungenutzter Import).
- noctx (net/http): http.NewRequestWithContext mit vorhandenem ctx.
- staticcheck: QF1001/S1009/ST1005/SA9003.
- contextcheck: detached-by-design-Stellen mit begründetem //nolint.

Zwei echte Bugs beim Aufräumen gefunden+gefixt:
- backup/remote SFTP-Upload: dst.Close()-Flush-Fehler wurde verschluckt →
  unvollständiges Remote-File galt als Erfolg. Jetzt geprüft+gemeldet.
- haproxy_test: leere if-Assertion (SA9003) testete faktisch nichts →
  echte t.Errorf-Prüfung (kein HSTS für HSTS-disabled Domain).

Bewusste Config-Entscheidungen (.golangci.yml):
- noctx-on-os/exec ausgeschlossen: System-Command-Reloads (systemctl/nft/
  wg/pg) dürfen NICHT an den Request-Context gebunden werden — ein Client-
  Disconnect darf keinen laufenden Reload mitten in der Ausführung killen.
  net/http-noctx bleibt voll aktiv. KEINE exec-Zeile im Code angefasst.
- rowserrcheck/sqlclosecheck raus (database/sql-Linter, bei pgx nur FPs).

Gate scharf gestellt: Makefile release-check ruft golangci-lint jetzt als
HARTEN Gate (install-if-missing, pinned v2.12.2). `make release-check`
grün: vet, golangci-lint, govulncheck, build, test -race.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/services/acme/acme.go

@@ -52,9 +52,6 @@ type Service struct {
 	AccountDir  string
 	DirURL      string
 	Email       string
-
-	// loaded lazily on first call
-	user *acmeUser
 }
 
 // New returns a Service with sensible defaults. Email comes from

internal/services/alerts/alerts.go

@@ -121,7 +121,7 @@ FROM alert_channels ORDER BY id ASC`)
 }
 
 func (s *Service) CreateChannel(ctx context.Context, c Channel) (*Channel, error) {
-	if c.Settings == nil || len(c.Settings) == 0 {
+	if len(c.Settings) == 0 {
 		c.Settings = json.RawMessage(`{}`)
 	}
 	row := s.Pool.QueryRow(ctx, `
@@ -138,7 +138,7 @@ RETURNING id, name, kind, target, settings, active, created_at, updated_at`,
 }
 
 func (s *Service) UpdateChannel(ctx context.Context, id int64, c Channel) (*Channel, error) {
-	if c.Settings == nil || len(c.Settings) == 0 {
+	if len(c.Settings) == 0 {
 		c.Settings = json.RawMessage(`{}`)
 	}
 	row := s.Pool.QueryRow(ctx, `
@@ -269,7 +269,7 @@ func (s *Service) sendWebhook(ctx context.Context, c Channel, kind string,
 	if err != nil {
 		return err
 	}
-	defer resp.Body.Close()
+	defer func() { _ = resp.Body.Close() }()
 	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
 		b, _ := io.ReadAll(io.LimitReader(resp.Body, 512))
 		return fmt.Errorf("webhook %d: %s", resp.StatusCode, strings.TrimSpace(string(b)))

internal/services/apt/apt.go

@@ -55,7 +55,7 @@ func PackageVersions(ctx context.Context, force bool) map[string]string {
 	defer cancel()
 
 	for _, pkg := range edgePackages {
-		installed, candidate := aptCachePolicy(policyCtx, pkg)
+		installed, candidate := aptCachePolicy(policyCtx, pkg) //nolint:contextcheck // detached by design — Cache-Read überlebt Request-Cancel
 		out[pkg+"_installed"] = installed
 		out[pkg+"_available"] = candidate
 	}

internal/services/backup/backup.go

@@ -30,7 +30,6 @@ import (
 	"os/exec"
 	"path/filepath"
 	"sort"
-	"strings"
 	"time"
 
 	"github.com/jackc/pgx/v5/pgxpool"
@@ -232,10 +231,9 @@ func (s *Service) Run(ctx context.Context, kind Kind, version string) (*Result,
 		s.recordFailure(ctx, res, hostname, kind)
 		return res, err
 	}
-	if err := f.Sync(); err != nil {
-		// Nicht fatal — fsync-failure kann passieren bei tmpfs in
-		// Dev, aber der File ist da.
-	}
+	// fsync best-effort — Nicht fatal: fsync-failure kann bei tmpfs in
+	// Dev passieren, der File ist trotzdem da.
+	_ = f.Sync()
 	if err := f.Close(); err != nil {
 		s.recordFailure(ctx, res, hostname, kind)
 		return res, err
@@ -644,10 +642,6 @@ func (b *bytes) Write(p []byte) (int, error) {
 	return len(p), nil
 }
 
-// strFold ist ein utility nur zum Defensiv-Check, dass kind ein
-// erlaubter Wert ist (für die DB-Constraint).
-func strFold(s string) string { return strings.ToLower(strings.TrimSpace(s)) }
-
 // SortByDate sortiert Entries newest-first. Wird nicht direkt benutzt
 // (DB-Query macht's), aber praktisch wenn der Caller eine eigene
 // Liste hat.

internal/services/backup/remote/remote.go

@@ -180,7 +180,7 @@ func uploadS3(ctx context.Context, s S3Settings, localPath string) (int64, error
 	if err != nil {
 		return 0, err
 	}
-	defer f.Close()
+	defer func() { _ = f.Close() }()
 	stat, err := f.Stat()
 	if err != nil {
 		return 0, err
@@ -245,12 +245,12 @@ func uploadSFTP(ctx context.Context, s SFTPSettings, localPath string) (int64, e
 	if err != nil {
 		return 0, fmt.Errorf("ssh dial %s: %w", addr, err)
 	}
-	defer conn.Close()
+	defer func() { _ = conn.Close() }()
 	cl, err := sftp.NewClient(conn)
 	if err != nil {
 		return 0, fmt.Errorf("sftp client: %w", err)
 	}
-	defer cl.Close()
+	defer func() { _ = cl.Close() }()
 
 	// remote-dir anlegen (idempotent)
 	_ = cl.MkdirAll(s.RemoteDir)
@@ -259,7 +259,7 @@ func uploadSFTP(ctx context.Context, s SFTPSettings, localPath string) (int64, e
 	if err != nil {
 		return 0, err
 	}
-	defer src.Close()
+	defer func() { _ = src.Close() }()
 	stat, err := src.Stat()
 	if err != nil {
 		return 0, err
@@ -269,10 +269,16 @@ func uploadSFTP(ctx context.Context, s SFTPSettings, localPath string) (int64, e
 	if err != nil {
 		return 0, fmt.Errorf("create remote: %w", err)
 	}
-	defer dst.Close()
 	if _, err := io.Copy(dst, src); err != nil {
+		_ = dst.Close()
 		return 0, fmt.Errorf("copy: %w", err)
 	}
+	// SFTP-Close flusht gepufferte Writes — ein Fehler hier bedeutet
+	// ein unvollständiges Remote-File und MUSS als Upload-Fehler
+	// gemeldet werden (nicht als Erfolg durchgehen).
+	if err := dst.Close(); err != nil {
+		return 0, fmt.Errorf("close remote: %w", err)
+	}
 	return stat.Size(), nil
 }
 
@@ -284,9 +290,9 @@ func (s *Service) Test(ctx context.Context, t Target) error {
 	if err != nil {
 		return err
 	}
-	defer os.Remove(tmp.Name())
+	defer func() { _ = os.Remove(tmp.Name()) }()
 	_, _ = tmp.WriteString("edgeguard remote-target test " + time.Now().Format(time.RFC3339))
-	tmp.Close()
+	_ = tmp.Close()
 
 	r := s.uploadOne(ctx, t, tmp.Name())
 	if !r.OK {
@@ -331,9 +337,9 @@ func (s *Service) Test(ctx context.Context, t Target) error {
 						HostKeyCallback: ssh.InsecureIgnoreHostKey(), Timeout: 5 * time.Second}); err == nil {
 					if cl, err := sftp.NewClient(conn); err == nil {
 						_ = cl.Remove(strings.TrimRight(settings.RemoteDir, "/") + "/" + filepath.Base(tmp.Name()))
-						cl.Close()
+						_ = cl.Close()
 					}
-					conn.Close()
+					_ = conn.Close()
 				}
 			}
 		}

internal/services/clusterjoin/join.go

@@ -5,6 +5,7 @@ package clusterjoin
 
 import (
 	"bytes"
+	"context"
 	"crypto/tls"
 	"crypto/x509"
 	"encoding/json"
@@ -177,7 +178,7 @@ func NormalizePrimaryURL(in string) (string, error) {
 
 func issueCert(primary, token, csr string, insecure bool) (caCert, peerCert string, err error) {
 	body, _ := json.Marshal(map[string]string{"token": token, "csr": csr})
-	req, err := http.NewRequest(http.MethodPost,
+	req, err := http.NewRequestWithContext(context.Background(), http.MethodPost,
 		primary+"/api/v1/cluster/issue-cert", bytes.NewReader(body))
 	if err != nil {
 		return "", "", err
@@ -193,7 +194,7 @@ func issueCert(primary, token, csr string, insecure bool) (caCert, peerCert stri
 	if err != nil {
 		return "", "", err
 	}
-	defer resp.Body.Close()
+	defer func() { _ = resp.Body.Close() }()
 	raw, _ := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
 	if resp.StatusCode != http.StatusOK {
 		return "", "", fmt.Errorf("HTTP %d: %s", resp.StatusCode, strings.TrimSpace(string(raw)))
@@ -287,7 +288,7 @@ func autoRegister(primary, tlsDir, commonName, version, nodeID, configHash, role
 	}
 	client := &http.Client{Transport: tr, Timeout: 30 * time.Second}
 
-	httpReq, err := http.NewRequest(http.MethodPost, u.String(), bytes.NewReader(body))
+	httpReq, err := http.NewRequestWithContext(context.Background(), http.MethodPost, u.String(), bytes.NewReader(body))
 	if err != nil {
 		return err
 	}
@@ -296,7 +297,7 @@ func autoRegister(primary, tlsDir, commonName, version, nodeID, configHash, role
 	if err != nil {
 		return err
 	}
-	defer resp.Body.Close()
+	defer func() { _ = resp.Body.Close() }()
 	raw, _ := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
 	if resp.StatusCode != http.StatusOK {
 		return fmt.Errorf("HTTP %d: %s", resp.StatusCode, strings.TrimSpace(string(raw)))

internal/services/firewall/addressgroups.go

@@ -97,7 +97,7 @@ func (r *AddressGroupsRepo) Create(ctx context.Context, g models.FirewallAddress
 	if err != nil {
 		return nil, err
 	}
-	defer tx.Rollback(ctx)
+	defer func() { _ = tx.Rollback(ctx) }()
 
 	row := tx.QueryRow(ctx, `
 INSERT INTO firewall_address_groups (name, description)
@@ -125,7 +125,7 @@ func (r *AddressGroupsRepo) Update(ctx context.Context, id int64, g models.Firew
 	if err != nil {
 		return nil, err
 	}
-	defer tx.Rollback(ctx)
+	defer func() { _ = tx.Rollback(ctx) }()
 
 	row := tx.QueryRow(ctx, `
 UPDATE firewall_address_groups SET name = $1, description = $2, updated_at = NOW()

internal/services/firewall/servicegroups.go

@@ -91,7 +91,7 @@ func (r *ServiceGroupsRepo) Create(ctx context.Context, g models.FirewallService
 	if err != nil {
 		return nil, err
 	}
-	defer tx.Rollback(ctx)
+	defer func() { _ = tx.Rollback(ctx) }()
 
 	row := tx.QueryRow(ctx, `
 INSERT INTO firewall_service_groups (name, description) VALUES ($1, $2)
@@ -115,7 +115,7 @@ func (r *ServiceGroupsRepo) Update(ctx context.Context, id int64, g models.Firew
 	if err != nil {
 		return nil, err
 	}
-	defer tx.Rollback(ctx)
+	defer func() { _ = tx.Rollback(ctx) }()
 
 	row := tx.QueryRow(ctx, `
 UPDATE firewall_service_groups SET name = $1, description = $2, updated_at = NOW()

internal/services/firewalllog/reader.go

@@ -102,7 +102,7 @@ func ReadTail(path string, f Filter) ([]Entry, error) {
 		}
 		return nil, err
 	}
-	defer file.Close()
+	defer func() { _ = file.Close() }()
 
 	// Ring-Buffer für die letzten f.Limit matching entries.
 	buf := make([]Entry, 0, f.Limit)

internal/services/firewalllog/tailer.go

@@ -64,7 +64,7 @@ func (t *Tailer) Start(ctx context.Context) error {
 	if err != nil {
 		return err
 	}
-	defer w.Close()
+	defer func() { _ = w.Close() }()
 
 	// Watch das Verzeichnis statt der Datei — wenn ulogd das File
 	// erstmals anlegt (oder rotate-rename), bekommen wir Create-Events.
@@ -106,7 +106,7 @@ func (t *Tailer) bootstrap() error {
 	if err != nil {
 		return err
 	}
-	defer f.Close()
+	defer func() { _ = f.Close() }()
 	sc := bufio.NewScanner(f)
 	sc.Buffer(make([]byte, 0, 64*1024), 1024*1024)
 	for sc.Scan() {
@@ -134,7 +134,7 @@ func (t *Tailer) drainFile() {
 	if err != nil {
 		return
 	}
-	defer f.Close()
+	defer func() { _ = f.Close() }()
 
 	stat, err := f.Stat()
 	if err != nil {

internal/services/wireguard/import.go

@@ -292,7 +292,7 @@ func parseWGConf(path string) (*parsedConf, error) {
 	if err != nil {
 		return nil, err
 	}
-	defer f.Close()
+	defer func() { _ = f.Close() }()
 
 	var (
 		out         parsedConf