8572d564b1
Completes the GenericPrinter -> BambuGenericPrinter -> BambuV1/V2 chain this project wanted from the start. BambuGenericPrinter holds the fields and behavior every Bambu printer shares (access code, serial number, CA trust, the TLS test/fetch methods); BambuV1Printer and BambuV2Printer each *have* one (composition) and are now genuinely separate types, ready to carry flavour-specific report-schema fields later. Also threads through a new 'sn' (serial number) field the real MQTT topics will need. Adds real 'fetch the CA automatically' capability, verified against a live TLS server (not just compiled): - BambuGenericPrinter::fetch_certificate() does trust-on-first-connect — connects once with verification disabled, captures the certificate the printer actually presents via native_tls's peer_certificate()/to_der(), and returns it as PEM. Deliberately a method you call once by hand (examples/fetch_bambu_cert.rs), not something connect() falls back to silently, since TOFU trusts whoever's on the network the moment you run it. Verified end-to-end against a local openssl s_server: the fetched PEM's SHA-256 fingerprint exactly matched the server's real certificate. - Verified the other direction too: test_bambu_certs (bundled-CA mode) correctly REJECTS that same test server's cert, since it wasn't signed by the real Bambu CA. Splitting BambuV1Printer/BambuV2Printer into distinct types broke the PrinterHandle::BambuV1(x) | PrinterHandle::BambuV2(x) or-pattern in both examples (or-patterns require every alternative to bind the same type) — fixed by giving each variant its own match arm.