Introduce watchdog and serialization improvements

- Added watchdog timer for improved system stability and responsiveness.
- Switched save data serialization to Bincode for better efficiency.
- Enhanced compatibility by supporting fallback to older JSON format.
- Improved logging during flash operations for easier debugging.
- Simplified SavegameManager by managing storage directly.

Software/MainBoard/rust/src/main.rs

@@ -749,6 +749,7 @@ pub async fn do_secure_pump(
                 }
                 None => Duration::from_millis(1),
             };
+            hal::PlantHal::feed_watchdog();
             Timer::after(sleep_time).await;
             pump_time_ms += 50;
         }
@@ -1119,6 +1120,8 @@ async fn wait_infinity(
 
         Timer::after_millis(delay).await;
 
+        hal::PlantHal::feed_watchdog();
+
         if wait_type == WaitType::MqttConfig && !MQTT_STAY_ALIVE.load(Ordering::Relaxed) {
             reboot_now.store(true, Ordering::Relaxed);
         }