Migrate serialization from Bincode to Postcard

- Replaced Bincode with Postcard for serialization/deserialization across configs and save operations.
- Simplified struct derives by removing `bincode`-specific traits.
- Updated `Cargo.toml` and `Cargo.lock` to include `postcard` and dependencies.
- Added padding stripping for deserialization and improved error handling.
- Adjusted serialization logic in `savegame_manager.rs` and related modules.

Software/MainBoard/rust/src/plant_state.rs

@@ -1,6 +1,5 @@
 use crate::hal::Moistures;
 use crate::{config::PlantConfig, hal::HAL, in_time_range};
-use bincode::{Decode, Encode};
 use chrono::{DateTime, TimeDelta, Utc};
 use chrono_tz::Tz;
 use serde::{Deserialize, Serialize};
@@ -73,7 +72,7 @@ impl PumpState {
     }
 }
 
-#[derive(Serialize, Deserialize, Clone, Copy, Debug, PartialEq, Encode, Decode)]
+#[derive(Serialize, Deserialize, Clone, Copy, Debug, PartialEq)]
 pub enum PlantWateringMode {
     Off,
     TargetMoisture,