refactor: carry out shade requests from one module behind a LoopQueue

HTTP routes and MQTT commands now both build a shade request and submit it
to the LoopQueue, which loop() drains into ShadeRequests. ShadeRequests
finds the shade or group, turns client positions into stored ones, checks
ranges and fills in default repeats, and reaches the shades through the
ShadeOps seam: SomfyShadeOps on the device, a recording fake in the native
tests. MqttCommands turns a .../set topic into a shade request.

Behaviour that changes:
- MQTT tiltTarget, mypos, myTiltPos and tiltPosition, and /setPositions,
  now honour flipPosition like the other routes.
- MQTT mypos keeps the favorite tilt (was set to 0) and myTiltPos keeps
  the favorite lift.
- repeat 0 on /shadeCommand means no repeats, as it did for groups; a
  JSON repeat over 127 is capped instead of wrapping to the default.
- Position corrections go through the setters, so MQTT publishes them.
- MQTT commands wait while the radio is full instead of being refused.
- The queue is drained every loop() pass and no longer from inside a
  GitHub firmware download.

WebCommand.h is replaced by LoopQueue.h and ShadeRequests.h. 45 new native
tests, 271 in all. Flash: esp32devdbg +976 bytes, esp32dev +1,380 bytes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

platformio.ini

@@ -109,7 +109,7 @@ lib_deps =
 platform = native
 test_framework = unity
 test_build_src = yes
-build_src_filter = -<*> +<Utils.cpp> +<SomfyFrame.cpp> +<JsonFormatter.cpp> +<ShadeMotion.cpp> +<ShadeSensors.cpp> +<PulseDecoder.cpp> +<TxBuffer.cpp> +<RadioScheduler.cpp>
+build_src_filter = -<*> +<Utils.cpp> +<SomfyFrame.cpp> +<JsonFormatter.cpp> +<ShadeMotion.cpp> +<ShadeSensors.cpp> +<PulseDecoder.cpp> +<TxBuffer.cpp> +<RadioScheduler.cpp> +<ShadeRequests.cpp> +<entryPoints/MqttCommands.cpp>
 build_flags =
 	-std=gnu++17
 	-Isrc