feat!: migrate firmware to DongLoRa Protocol v2 wire format

Wire-incompatible break with the 0.x protocol. Every host-side path (UART, USB CDC, framing, radio dispatcher, display update channel) speaks the v2 wire format defined in PROTOCOL.md.

* Replace the host framing path with streaming FrameDecoder + encode_frame from donglora-protocol, matching the new (type_id, tag, payload) shape.

* Update src/channel.rs and src/host/{uart,usb,framing}.rs for the new frame semantics: per-request tag echo, CRC checked in the decoder, async ERR fan-out on tag 0.

* Rework src/radio.rs to emit RX / TX_DONE / OK / ERR messages in v2 shape, including RxOrigin, TxDonePayload, and SetConfigResult codes.

* Update src/protocol.rs glue to re-export v2 types from donglora-protocol and drop the legacy 0.x shim surface.

* Refresh PROTOCOL.md to the v2 normative spec (kept in sync with the donglora-protocol crate).

* Minor display and main-loop cleanups needed for the new radio event shape.

Cargo.lock

@@ -1389,6 +1389,7 @@ version = "0.9.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2af2455f757db2b292a9b1768c4b70186d443bcb3b316252d6b540aec1cd89ed"
 dependencies = [
+ "defmt 1.0.1",
  "hash32",
  "stable_deref_trait",
 ]