Use VecDeque for tasks and marked cells

Replace `Vec` with `VecDeque` in `BoardState` marked cells,
`DiggingTask` path,
and `MinerUnit` tasks to enable efficient push/pop operations. Remove
the
`Copy` trait from several structs and enums, adjust derives accordingly,
and
use `as_ref` in `Option<Units>` implementations to avoid consuming the
option.
Update cell rendering to clone widgets and adjust
`CellWidget::get_option_unit`
to return a cloned `Option<Units>`. Add necessary `VecDeque` imports.

src/app/states/skirmish_states/units/miner.rs

@@ -1,12 +1,13 @@
 use crate::app::states::skirmish_states::{Players, tasks::Tasks, units::Unit};
+use std::collections::VecDeque;
 
-#[derive(Debug, Clone, Copy, PartialEq)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct MinerUnit {
     owner: Players,
     hp: u16,
     can_dig: bool,
     digging_power: f32,
-    // tasks: Vec<Tasks>,
+    pub tasks: VecDeque<Tasks>,
 }
 
 impl MinerUnit {
@@ -16,7 +17,7 @@ impl MinerUnit {
             hp: 100,
             can_dig: true,
             digging_power: 0.55,
-            // tasks: Vec::new(),
+            tasks: VecDeque::new(),
         }
     }
 }