Removed adapters/ (rumqttc MQTT, suppaftp FTPS, reqwest HTTP), plate_changer/
(tokio-serial), discovery/, and cache.rs (rusqlite) — src/printer/ already
covers 'talk to a printer' as simple stubs, so keeping a second, more complex
version alongside it was redundant. main.rs goes from 6 concurrent tasks to
2 (uplink + go2rtc). uplink/ drops channels, jitter, and Send-bound futures.
Verified with cargo build + cargo run --example printer_polymorphism.
Drop reqwest, RPITIT+Send signature, and multi-variant error enum from the
teaching example so the only new idea per file is the trait override itself.
Real networking stays in adapters/, unaffected.
octoturge
