fix: remediate severity-ordered review findings across cache, scanners, and proxies

- H2: gormstore soft-delete + storage_key UNIQUE collision; re-save after eviction succeeds
- H1: cache getOrFetch cache-hit branch no longer runs CheckVulnerabilities on metadata entries
- M2: cache store() streams upstream body to temp file + SHA256 instead of double-buffering
- H3/L3: FetchResult/FetchFunc plumbing (+RequiresAuth/AuthProvider); proxy closures adapted;
        goproxy strips git+ prefix from UpstreamURL
- H4: scanner normalizes bypass package names; CheckVulnerabilities builds normalized packageKey
- M4: requireAdmin routes through extractAPIKey -> ValidateAPIKey -> admin role check
- M5: network client keeps only final RecordFailure (one count per attempt cycle)
- M3: normalizeOriginHost + buildCheckOrigin rewrite; origin_test.go added
- M1: app lifecycle cancel func; Run -> Shutdown on listen error (sole cache owner); JoinHostPort
- M6: VulnerabilityThresholds defaults all -1 so BlockOnSeverity governs
- L4: metadata.NormalizeSeverity at 4 severity-count sites (MEDIUM->MODERATE consistency)
- L1: handleDeleteBypass uses structured *errors.Error + ErrCodeNotFound
- L2: pypi extractVersionFromFilename (wheel/2nd segment, non-wheel/last digit segment);
      cacheVersion uses full unique basename; regression tests added
- L5: document per-instance ValidationCache key scoping; rename packageURL param to resource

All: go build ./... && go vet ./... && go test ./... pass; golangci-lint clean.

pkg/auth/validator.go

@@ -18,6 +18,9 @@ type CredentialValidator interface {
 	// ValidateAccess checks if credentials grant access to a package
 	// Returns (allowed bool, error)
 	ValidateAccess(ctx context.Context, packageURL string, credentials string) (bool, error)
+	// Provider returns the upstream auth provider identifier stored on
+	// packages that require auth (e.g. github, gitlab, npm, pypi).
+	Provider() string
 }
 
 // NPMValidator validates npm registry credentials
@@ -36,6 +39,11 @@ func NewNPMValidator() *NPMValidator {
 	}
 }
 
+// Provider identifies this validator's upstream provider.
+func (v *NPMValidator) Provider() string {
+	return "npm"
+}
+
 // ValidateAccess validates npm package access using HEAD request
 func (v *NPMValidator) ValidateAccess(ctx context.Context, packageURL string, credentials string) (bool, error) {
 	req, err := http.NewRequestWithContext(ctx, "HEAD", packageURL, nil)
@@ -87,6 +95,11 @@ func NewPyPIValidator() *PyPIValidator {
 	}
 }
 
+// Provider identifies this validator's upstream provider.
+func (v *PyPIValidator) Provider() string {
+	return "pypi"
+}
+
 // ValidateAccess validates PyPI package access using HEAD request
 func (v *PyPIValidator) ValidateAccess(ctx context.Context, packageURL string, credentials string) (bool, error) {
 	req, err := http.NewRequestWithContext(ctx, "HEAD", packageURL, nil)
@@ -134,6 +147,26 @@ func NewGoValidator() *GoValidator {
 	}
 }
 
+// Provider returns the base upstream provider identifier used when the
+// registry does not distinguish hosts (e.g. a generic git host).
+func (v *GoValidator) Provider() string {
+	return "git"
+}
+
+// ProviderFor derives the specific provider identifier from a module path.
+// Mirrors the host branching in ValidateAccess so the stored AuthProvider
+// reflects the actual upstream host (github, gitlab, or a generic git host).
+func (v *GoValidator) ProviderFor(modulePath string) string {
+	switch {
+	case strings.HasPrefix(modulePath, "github.com/"):
+		return "github"
+	case strings.HasPrefix(modulePath, "gitlab.com/"):
+		return "gitlab"
+	default:
+		return "git"
+	}
+}
+
 // ValidateAccess validates Go module access using git ls-remote
 func (v *GoValidator) ValidateAccess(ctx context.Context, modulePath string, credentials string) (bool, error) {
 	// Create context with timeout