feat(02-06): wire all Phase 2 modules into asyncio REPL entry point

- Create src/led_sync/main.py with AppState, handle_command, repl, async_main, main
- Implements all D-13 REPL commands: play/pause/resume/seek/stop/load/add/save/status/beat/help/quit
- Create src/led_sync/__main__.py for python -m led_sync invocation
- Add led-sync script entry point to pyproject.toml
- Wires AudioPlayer, ChoreographyScheduler, BeatDetector, ESP32Transport

pyproject.toml

@@ -15,6 +15,9 @@ dependencies = [
 requires = ["hatchling"]
 build-backend = "hatchling.build"
 
+[project.scripts]
+led-sync = "led_sync.main:main"
+
 [tool.hatch.build.targets.wheel]
 packages = ["src/led_sync"]