fix(security): x/crypto v0.52 + x/net v0.55 (6 CVEs) + govulncheck-Release-Gate — v1.3.1

govulncheck ab sofort fest im Release-Prozess. Baseline-Scan fand 6 aktiv
aufgerufene Vulns (SSH-Backup-Pfad internal/services/backup/remote):
- 5× golang.org/x/crypto (SSH DoS/Deadlock/Panic: GO-2026-5013/5017/5018/5019/5020)
  → x/crypto v0.51.0 => v0.52.0
- 1× golang.org/x/net (GO-2026-5026) → v0.53.0 => v0.55.0
Re-Scan danach: "No vulnerabilities found."

Go-Quality-Baseline (Makefile + .golangci.yml, portabel):
- release-check läuft autom. vor jedem deb/publish: vet → golangci-lint
  (Rollout: non-blocking) → govulncheck (HARTER Gate) → build → test -race.
- make vulncheck / make test-race als eigene Targets.
- .golangci.yml: staticcheck/govet/errcheck/ineffassign/unused/misspell +
  gosec/bodyclose/rowserrcheck/sqlclosecheck/noctx/contextcheck.
- go test -race: aktuell 0 Races (Gate sicher).
Doku in CLAUDE.md.

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

Makefile

@@ -10,7 +10,7 @@ LDFLAGS  := -s -w -X main.version=$(VERSION)
 GOFLAGS  := -trimpath -mod=readonly
 export CGO_ENABLED ?= 0
 
-.PHONY: all help build test lint tidy clean ui \
+.PHONY: all help build test test-race lint vulncheck release-check tidy clean ui \
         build-linux-amd64 build-linux-arm64 \
         deb deb-amd64 deb-arm64 \
         publish publish-amd64 publish-arm64
@@ -61,9 +61,35 @@ build-linux-arm64:
 test:
 	$(GO) test $(GOFLAGS) ./...
 
+test-race:
+	CGO_ENABLED=1 $(GO) test $(GOFLAGS) -race ./...
+
 lint:
 	$(GO) vet ./...
-	@command -v staticcheck >/dev/null && staticcheck ./... || echo "staticcheck not installed, skipping"
+	@command -v golangci-lint >/dev/null 2>&1 && golangci-lint run \
+	  || echo "golangci-lint nicht installiert (go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@latest) — übersprungen"
+
+GOBIN := $(shell $(GO) env GOPATH)/bin
+
+# govulncheck — Go-Vuln-DB-Scan. HARTER Release-Gate: bricht ab, wenn der
+# Code eine bekannte Vulnerability tatsächlich aufruft. Tool wird bei Bedarf
+# automatisch installiert.
+vulncheck:
+	@command -v govulncheck >/dev/null 2>&1 || GOFLAGS= $(GO) install golang.org/x/vuln/cmd/govulncheck@latest
+	@PATH="$(GOBIN):$$PATH" govulncheck ./...
+
+# Go-Quality-Baseline — läuft automatisch vor jedem Release (deb/publish).
+# Reihenfolge: vet → golangci-lint (Rollout: NON-BLOCKING) → govulncheck (GATE)
+# → build → test -race. govulncheck bricht bei jedem Fund ab; der Linter ist
+# in der Rollout-Phase noch non-blocking (Bestand aufräumen, dann auf Gate).
+release-check:
+	$(GO) vet ./...
+	@command -v golangci-lint >/dev/null 2>&1 && (golangci-lint run || echo "  ⚠ golangci-lint-Findings (non-blocking, Rollout-Phase)") \
+	  || echo "  golangci-lint nicht installiert — übersprungen (Rollout-Phase)"
+	@$(MAKE) --no-print-directory vulncheck
+	$(GO) build ./...
+	CGO_ENABLED=1 $(GO) test $(GOFLAGS) -race ./...
+	@echo "  ✓ Go-Quality-Baseline bestanden (vet, govulncheck, build, test -race)"
 
 tidy:
 	$(GO) mod tidy
@@ -74,10 +100,10 @@ ui:
 	    if [ -x "$$(command -v bun)" ]; then bun install --silent && bun run build; \
 	    else npm install --silent && npm run build; fi
 
-deb-amd64: build-linux-amd64 ui
+deb-amd64: release-check build-linux-amd64 ui
 	@./scripts/apt-repo/build-package.sh amd64 $(VERSION)
 
-deb-arm64: build-linux-arm64 ui
+deb-arm64: release-check build-linux-arm64 ui
 	@./scripts/apt-repo/build-package.sh arm64 $(VERSION)
 
 deb: deb-amd64 deb-arm64