Refactor DiggingTask and embed it in Tasks enum

- Remove lifetime and path storage from DiggingTask, make it Copy.
- Add a placeholder `new` constructor that accepts a path.
- Update the Tasks enum to hold a DiggingTask value.
- Reorder module declarations and re‑export order for tasks.
- Add a commented‑out tasks field to MinerUnit as a preparation step.

src/app/states/skirmish_states/tasks/digging.rs

@@ -1,6 +1,14 @@
 use crate::app::widgets::CellWidget;
 
-#[derive(Debug, Clone, PartialEq)]
-pub struct DiggingTask<'a> {
-    path: Vec<&'a CellWidget>,
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct DiggingTask {
+    // path: Vec<(usize, usize)>,
+}
+
+impl DiggingTask {
+    pub fn new(path: Vec<(u16, u16)>) -> Self {
+        Self {
+            // path
+        }
+    }
 }