feat: add fertilizer cooldown functionality with web UI, HAL integration, and configuration support

Software/MainBoard/rust/src/plant_state.rs

@@ -89,6 +89,8 @@ pub struct PlantState {
     pub sensor_a_firmware_build_minutes: Option<u32>,
     /// Last known firmware build timestamp for sensor B.
     pub sensor_b_firmware_build_minutes: Option<u32>,
+    /// Last time fertilizer was applied (Unix timestamp in seconds).
+    pub last_fertilizer_time: i64,
 }
 
 fn map_range_moisture(
@@ -162,6 +164,7 @@ impl PlantState {
 
         let previous_pump = board.board_hal.get_esp().last_pump_time(plant_id);
         let consecutive_pump_count = board.board_hal.get_esp().consecutive_pump_count(plant_id);
+        let last_fertilizer_time = board.board_hal.get_esp().last_fertilizer_time(plant_id);
         let (a_builds, b_builds) = board.board_hal.get_sensor_build_minutes();
         let state = Self {
             sensor_a,
@@ -172,6 +175,7 @@ impl PlantState {
             },
             sensor_a_firmware_build_minutes: a_builds[plant_id],
             sensor_b_firmware_build_minutes: b_builds[plant_id],
+            last_fertilizer_time,
         };
         if state.is_err() {
             let _ = board.board_hal.fault(plant_id, true).await;
@@ -296,6 +300,7 @@ impl PlantState {
             },
             sensor_a_firmware_build_minutes: self.sensor_a_firmware_build_minutes,
             sensor_b_firmware_build_minutes: self.sensor_b_firmware_build_minutes,
+            last_fertilizer_time: self.last_fertilizer_time
         }
     }
 }
@@ -328,4 +333,6 @@ pub struct PlantInfo<'a> {
     sensor_a_firmware_build_minutes: Option<u32>,
     /// firmware build timestamp of sensor B (minutes since Unix epoch); None if unknown
     sensor_b_firmware_build_minutes: Option<u32>,
+    /// last time when fertilizer was applied
+    last_fertilizer_time: i64,
 }