feat: end-to-end app controller integration and tests

Add app_controller wiring UART, integration, status monitor and Zigbee
ZCL layers together with command/feedback flows and reset/recovery.
Add main.c entry point (guarded for test builds), app_controller_test
integration tests (full command cycle, timing under load, recovery),
Makefile target, and Readme updates.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/plans/2026-07-05-ballu-ac-esp32c6-controller-implementation.md

@@ -71,13 +71,13 @@ Implementation of ESP32-C6 based AC controller that bridges Zigbee (Home Assista
 - [x] Update Readme.md
 
 ### Task 6: End-to-End Integration and Testing
-- [ ] Integrate all layers: Zigbee ←→ Integration ←→ UART
-- [ ] Test command flow: HA → Zigbee → UART → AC → Status → Zigbee → HA
-- [ ] Validate timing constraints under load
-- [ ] Implement reset/recovery procedures
-- [ ] Write integration tests for full command cycles
-- [ ] Run full test suite - must pass before completion
-- [ ] Update Readme.md
+- [x] Integrate all layers: Zigbee ←→ Integration ←→ UART
+- [x] Test command flow: HA → Zigbee → UART → AC → Status → Zigbee → HA
+- [x] Validate timing constraints under load
+- [x] Implement reset/recovery procedures
+- [x] Write integration tests for full command cycles
+- [x] Run full test suite - must pass before completion
+- [x] Update Readme.md
 
 ### Task 7: Documentation and Validation
 - [ ] Update CLAUDE.md with implementation details