storage SAT: fix NVMe SMART counters showing 0 for power-on hours/read/write

nvme-cli emits large 64-bit counters as JSON-quoted strings on some
versions; the disk-report text generator only handled bare numbers and
{lo,hi} objects, so power_on_hours/data_units_read/data_units_written
etc. silently parsed as 0 while the structured collector path already
handled this correctly. Unify both paths on a single exported
JSONInt64/NVMeSmartLog/NVMeIDCtrl type in collector/storage.go instead
of keeping two independent nvme-cli JSON parsers in sync.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

audit/internal/collector/storage_discovery_test.go

@@ -56,7 +56,7 @@ func TestJsonInt64UnmarshalBothFormats(t *testing.T) {
 		{`null`, 0},
 	}
 	for _, tc := range cases {
-		var v jsonInt64
+		var v JSONInt64
 		if err := v.UnmarshalJSON([]byte(tc.json)); err != nil {
 			t.Fatalf("UnmarshalJSON(%s): unexpected error %v", tc.json, err)
 		}