feat: Add PROFILE command — heap, stack watermarks, CPU runtime stats

- PROFILE command returns heap usage (free/min/dram/iram),
  per-task stack high watermark, and per-task CPU % (when
  CONFIG_FREERTOS_GENERATE_RUN_TIME_STATS is enabled)
- Enable FreeRTOS runtime stats in sdkconfig.defaults
- Enlarge cmd reply buffer to 1400 bytes for multi-line output
- Add esp_heap_caps.h include

get-started/csi_recv_router/sdkconfig.defaults

@@ -35,6 +35,8 @@ CONFIG_COMPILER_OPTIMIZATION_PERF=y
 # FreeRTOS
 #
 CONFIG_FREERTOS_HZ=1000
+CONFIG_FREERTOS_GENERATE_RUN_TIME_STATS=y
+CONFIG_FREERTOS_USE_STATS_FORMATTING_FUNCTIONS=y
 
 #
 # ESP32-specific