feat: Add OLED size build flag support and implement PowerManager for enhanced power management

README.md

@@ -15,3 +15,19 @@ ESP32 + SH1106 OLED + soil moisture buddy with expressions.
 ## Wiring
 - OLED (I2C): SDA=GPIO21, SCL=GPIO22, VCC=3.3V, GND=GND
 - Moisture sensor analog out: GPIO34
+
+## OLED Size Build Flag
+FacePlant now supports compile-time OLED profiles via `PB_OLED_SIZE`:
+- `96` for 0.96" OLED
+- `130` for 1.3" OLED
+- `240` for 2.4" OLED
+
+Predefined PlatformIO environments:
+- `esp32-s3-oled-096`
+- `esp32-s3-oled-130`
+- `esp32-s3-oled-240`
+
+Example:
+```bash
+pio run -e esp32-s3-oled-240 -t upload
+```