Virtual gearing, trainer-speed blend, and cadence decode

Gears are expressed as an offset to the commanded gradient, leaving the
physics on the route's true gradient so shifting changes effort, not speed.
Neutral gear commands exactly the route gradient, so an un-shifted ride is
unchanged.

Cadence is not in FTMS on this trainer but is on its Zwift channel, decoded
against captured frames. The undeclared FTMS trailing bytes were ruled out:
wheel RPM restated at a fixed 73.8x speed.

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

Cargo.lock

@@ -119,6 +119,7 @@ name = "bikecontrol-app"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "bikecontrol-ble",
  "bikecontrol-core",
  "roxmltree",
  "serde",
@@ -131,6 +132,7 @@ dependencies = [
  "tokio",
  "tracing",
  "tracing-subscriber",
+ "uuid",
 ]
 
 [[package]]