Offline structural validator for an Indian CIN (Corporate Identity Number, 21 characters). Parses and checks: listing status letter (L/U), 5-digit NIC industry code, 2-letter state code (against the known MCA state-code list), 4-digit incorporation year (plausible range), 3-letter company-type/ownership code (against a known enum like PLC, PTC, OPC, GOI, NPL, FTC, SGC, ULL, ULT), and 6-digit regis