Adjust timeouts and constants for improved moisture sensor and backup management accuracy

- Increased CAN measurement timeout to 5000ms for reliability.
- Updated `SAVEGAME_SLOT_SIZE` usage in backup handling for consistency.
- Refined moisture sensor frequency thresholds for better sensor calibration (400Hz-70kHz).

Software/MainBoard/rust/src/webserver/backup_manager.rs

@@ -1,4 +1,5 @@
 use crate::fat_error::{FatError, FatResult};
+use crate::hal::savegame_manager::SAVEGAME_SLOT_SIZE;
 use crate::webserver::read_up_to_bytes_from_request;
 use crate::BOARD_ACCESS;
 use alloc::borrow::ToOwned;
@@ -46,7 +47,7 @@ pub(crate) async fn backup_config<T, const N: usize>(
 where
     T: Read + Write,
 {
-    let input = read_up_to_bytes_from_request(conn, Some(4096)).await?;
+    let input = read_up_to_bytes_from_request(conn, Some(SAVEGAME_SLOT_SIZE)).await?;
     info!("Read input with length {}", input.len());
     let mut board = BOARD_ACCESS.get().await.lock().await;
     let config_to_backup = serde_json::from_slice(&input)?;