Reduce sender power draw (RX windows + CPU/WiFi/ADC/pins)

- Add LoRa idle/sleep/receive-window helpers and use short RX windows for ACK/time sync

- Schedule sender time-sync windows (fast/slow) and track RX vs sleep time in debug

- Lower sender power (80 MHz CPU, WiFi/BT off, reduced ADC sampling, unused pins pulldown)

- Make SERIAL_DEBUG_MODE a build flag, add prod envs with debug off, and document changes

platformio.ini

@@ -18,6 +18,8 @@ lib_deps =
   adafruit/Adafruit SSD1306@^2.5.9
   adafruit/Adafruit GFX Library@^1.11.9
   knolleary/PubSubClient@^2.8
+build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
 
 [env:lilygo-t3-v1-6-1-test]
 platform = https://github.com/pioarduino/platform-espressif32/releases/download/51.03.07/platform-espressif32.zip
@@ -30,6 +32,7 @@ lib_deps =
   adafruit/Adafruit GFX Library@^1.11.9
   knolleary/PubSubClient@^2.8
 build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
   -DENABLE_TEST_MODE
 
 [env:lilygo-t3-v1-6-1-868]
@@ -43,6 +46,7 @@ lib_deps =
   adafruit/Adafruit GFX Library@^1.11.9
   knolleary/PubSubClient@^2.8
 build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
   -DLORA_FREQUENCY_HZ=868E6
 
 [env:lilygo-t3-v1-6-1-868-test]
@@ -56,6 +60,7 @@ lib_deps =
   adafruit/Adafruit GFX Library@^1.11.9
   knolleary/PubSubClient@^2.8
 build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
   -DENABLE_TEST_MODE
   -DLORA_FREQUENCY_HZ=868E6
 
@@ -70,6 +75,7 @@ lib_deps =
   adafruit/Adafruit GFX Library@^1.11.9
   knolleary/PubSubClient@^2.8
 build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
   -DPAYLOAD_CODEC_TEST
 
 [env:lilygo-t3-v1-6-1-868-payload-test]
@@ -83,5 +89,33 @@ lib_deps =
   adafruit/Adafruit GFX Library@^1.11.9
   knolleary/PubSubClient@^2.8
 build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
   -DPAYLOAD_CODEC_TEST
   -DLORA_FREQUENCY_HZ=868E6
+
+[env:lilygo-t3-v1-6-1-prod]
+platform = https://github.com/pioarduino/platform-espressif32/releases/download/51.03.07/platform-espressif32.zip
+board = ttgo-lora32-v1
+framework = arduino
+lib_deps =
+  sandeepmistry/LoRa@^0.8.0
+  bblanchon/ArduinoJson@^6.21.5
+  adafruit/Adafruit SSD1306@^2.5.9
+  adafruit/Adafruit GFX Library@^1.11.9
+  knolleary/PubSubClient@^2.8
+build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=0
+
+[env:lilygo-t3-v1-6-1-868-prod]
+platform = https://github.com/pioarduino/platform-espressif32/releases/download/51.03.07/platform-espressif32.zip
+board = ttgo-lora32-v1
+framework = arduino
+lib_deps =
+  sandeepmistry/LoRa@^0.8.0
+  bblanchon/ArduinoJson@^6.21.5
+  adafruit/Adafruit SSD1306@^2.5.9
+  adafruit/Adafruit GFX Library@^1.11.9
+  knolleary/PubSubClient@^2.8
+build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=0
+  -DLORA_FREQUENCY_HZ=868E6